Communication apparatus and communication method

ABSTRACT

A communication apparatus comprises a generator that generates frequency resource position information corresponding to a first information which is based on the communication quality information received from user equipments, the frequency resource position information indicating validity or invalidity of the first information for each frequency resource, and 
     a transmitter that transmits the first information, the frequency resource position information and a cell ID which the frequency resource position is applied, to another communication apparatus via a backhaul.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of the non-provisional applicationSer. No. 13/520,406 which is a national phase of the internationalapplication No. PCT/JP2011/000060 filed Jan. 7, 2011 which claims thepriority of Japanese patent application No. 2010-003332, filed Jan. 8,2010, the contents of which are incorporated by reference in itsentirety. application Ser. No. 13/520,406 issued as U.S. Pat. No.9,137,685.

TECHNICAL FIELD

The present invention relates to a communication apparatus and acommunication method for notifying other communication apparatuses ofprecoding information via a backhaul.

BACKGROUND ART

As a mobile communication system that succeeds an LTE (Long TermEvolution), standardization of an LTE-advanced in the 3GPP (ThirdGeneration Partnership Project) has been reviewed. In the LTE-advanced,for the purpose of an improvement in a user throughput of UE (UserEquipment) that is located at a cell edge, an improvement in a cellthroughput, or the like, a review has been made with respect to atechnology in which a plurality of transmission and reception pointsthat are geographically distant from each other cooperate with eachother and perform a MIMO (Multi-Input Multi-Output) transmission, whichis called coordinated multi-point transmission and reception (CoMP),even in a downlink (DL) and an uplink (UL). The CoMP is classified intothe following two technologies (A) and (B). Hereinafter, the userequipment is sometimes expressed by an UE.

(A) Joint Processing (JP)

In the joint processing, data transmitted to the UEs may be used at theplurality of CoMP transmission points, and is transmitted as a desiredsignal toward the UEs. In this way, large inter-cell interference (ICI)from neighbor cells is changed into a desired signal, and other-cellinterference is reduced. In addition, as a sub-category of the jointprocessing, Joint Transmission (JT)/Dynamic Cell Selection (DCS) isdefined.

(B) Coordinated Beamforming (CB) and Coordinated Scheduling (CS)

In the coordinated beamforming and the coordinated scheduling, data thatis transmitted to the UEs may be used only by a serving cell, and istransmitted only from the serving cell. In addition, information such asa beamforming weight that is necessary for the coordinated schedulingand the coordinated beamforming is determined in a coordination manneramong the plurality of transmission points. Therefore, the inter-cellinterference may be effectively reduced or suppressed.

Both of the joint processing and the coordinated beamforming methods areeffective technologies to realize high frequency usage efficiency.

As described above, in the LTE-advanced, an approach has been made withrespect to a situation in which due to the coordinated MIMO transmissionand reception technologies among the plurality of the transmission andreception points (for example, NodeB), inter-cell interference isreduced and therefore the high frequency usage efficiency is realized.On the other hand, in Rel. 8 description of the LTE, a configuration isalso defined to realize Inter-Cell Interference Coordination (ICIC).Hereinafter, a downlink (DL) transmission from a base station to theuser equipment will be described.

In the DL transmission of the LTE Rel. 8, an RNTP (Relative Narrow bandTX Power), which indicates information of future transmission signalpower (normalized EPRE (Energy Per Resource Element)) in physicalresource block (PRB) units, is defined as a binary indicator (0 or 1)(refer to Non-Patent Literature 3).

Here, 1 PRB is made up by 12 resource elements (RE), that is, 12sub-carriers. Due to an inter-cell coordinated scheduling in which anindicator of future transmission signal power (RNTP) in other cells isused, the ICIC in a frequency domain may be realized. Hereinafter, thephysical resource block is sometimes expressed simply by a PRB.

FIG. 22A shows a conceptual diagram of a case in which the indicator ofthe RNTP is shared between cells. In addition, FIG. 22(B) shows theindicator of the RNTP for each PRB in a frequency domain.

As shown in FIG. 22A, NodeB #0 (serving cell) notifies NodeB #1(non-serving cell) of the indicator of the RNTP via a backhaul (forexample, X2 interface). In addition, the NodeB #1 performs thecoordinated scheduling of the frequency domain by using the indicator ofthe RNTP of the NodeB #0.

In addition, as shown in FIG. 22(B), the indicator of the RNTP isinformation of future transmission signal power for each PRB. In a casewhere a normalized EPRE (transmission signal power density) is smallerthan any RNTP threshold value (that is, the transmission signal power isreduced in the future), the indicator of the RNTP shows “0”. Inaddition, the upper limit of the normalized EPRE is not promised (nopromise), the indicator of the RNTP shows “1”.

That is, the NodeB #0 notifies the NodeB #1 of information of thetransmission signal power for each PRB, for example, via the backhaulsuch as X2, and the NodeB that has received the information does notallocate the UE of a serving cell to the PRB showing the indicator of 1and may perform the coordinated scheduling of the frequency domain, inwhich interference with neighbor cells is reduced. That is, the NodeB #0may effectively realize an FFR (Fractional Frequency Reuse) byconsidering other-cell interference.

However, in the transmission system of LTE Rel. 8, an effect of reducinginterference with other cells and a decrease in the frequency usageefficiency through the sharing of a band between cells are in atrade-off relationship, such that there is a problem in that animprovement effect of the throughput is not sufficient. Here, the“sharing of a band between cells” is equivalent to a case in whichfrequency repetition (reuse factor) is partially set to be more than 1in the system band.

Therefore, as described above, in the LTE-advanced, a review has beenmade with respect to the inter-cell interference coordination (ICIC) onthe same time-frequency, which uses a spatial domain (MIMO of aplurality of transmission and reception points that are geographicallydistant from each other). As a method of controlling interferencebetween coordination cells by using the spatial domain, the followingmethod has been reviewed (for example, refer to Non-Patent Literature 1and Non-Patent Literature 2).

In a Single-User (SU)-MIMO in a single cell or a Multi-User (MU)-MIMO inthe related art, when selecting a precoding matrix indicator (PMI),which is defined for precoding (beamforming) of a transmission signal,only a precoding (beamforming) in a serving cell to which user equipmentof a serving cell is connected is taken into consideration. In addition,a method in which the user equipment selects a PMI that is capable ofmaximizing the throughput (that is, Best PMI) and feeds back the PMI toa serving cell has been adopted. On the other hand, in Non-PatentLiterature 1 and Non-Patent Literature 2, on the basis of extendedfeedback information related to the PMI (beamforming weight) from the UEin which interference from other cells is taken into consideration, thePMI information (for example, a PMI restricting the use in neighborcells, that is, worst PMI) is shared between coordination nodes. Inaddition, on the basis of the shared information, the coordinatedbeamforming (CB) is performed among the plurality of cells, and therebythe maximization of the throughput in the entirety of the plurality ofcells is attempted. Hereinafter, specific means thereof will beillustrated with reference to FIG. 23. FIG. 23 shows a conceptualdiagram in a case where the coordinated beamforming (CB) among theplurality of cells is performed on the basis of the PMI information.

(1) The UE receives a reference signal (RS) of other cells (and aserving cell) and determines a worst PMI list of other cells thatgenerate large inter-cell interference (ICI) with itself. In addition,the UE feeds back the worst PMI list (worst PMI #0 and worst PMI #3 inthe drawing) to the serving cell (refer to arrow (1) in FIG. 23).

(2) The NodeB #0 that is a serving-cell selects the worst PMI list onthe basis of feedback information from a plurality of UEs that areconnected to the serving cell, and notifies other nodes of the selectedworst PMI list (refer to arrow (2)-2 in FIG. 23).

(3) Other nodes select a PMI other than the notified worst PMI andtransmit it to the UE in the serving cell (connected to the node) in aprecoding (beamforming) manner (refer to (3) in FIG. 23).

In this manner, interference with neighbor cells may be reduced whileavoiding the decrease in frequency usage efficiency by sharing the bandbetween the coordination cells (the number of frequency repetitions(reuse factor) is partially set to be more than 1 in the system band),which is a problem in the transmission system of LTE Rel. 8.

CITATION LIST Non Patent Literature

Non-Patent Literature 1: R1-093780, Estimation of extended PMI feedbacksignaling required for user intra-cell and inter-cell coordination, 3GPPTSG RAN WG1 #58bis, Miyazaki, Japan, 12-16 Oct. 2009

Non-Patent Literature 2: R1-093781, Consideration on performance ofcoordinated beamforming with PMI feedback, 3GPP TSG RAN WG1 #58bis,Miyazaki, Japan, 12-16 Oct. 2009

Non-Patent Literature 3: 3GPP TS 36.213 V8.7.0 (2009-05)

SUMMARY OF INVENTION Technical Problem

When the transmission system in Non-Patent Literature 1 and Non-PatentLiterature 2 described above is extended to a frequency domain,inter-cell interference coordination (ICIC) of a frequency domain and aspatial domain may be easily assumed. For example, other nodes arenotified of an extended PMI (beamforming weight) list for each sub-bandthat is made up by one PRB or a plurality of PRBs through a backhaul,other nodes that have received this information select a PMI other thanthe extended PMI (for example, worst PMI), which is notified for eachPRB, and other nodes transmit the selected PMI toward UEs connected tothe cells in a precoding (beamforming) manner. Here, the worst PMI is anexample of the extended PMI, and is an indicator of the precoding weightthat is not desired to use by adjacent nodes.

In this manner, an appropriate beamforming weight for each band may beselected between coordination nodes, and therefore the inter-cellinterference coordination (ICIC) may be effectively reduced. FIG. 24shows an example of a transmission system to effectively reduce theinter-cell interference coordination (ICIC). As shown in FIG. 24, on thebasis of the extended PMI information (worst PMI information) that isfed back from a plurality of UEs that are connected to the NodeB #0, theNodeB #0 separately selects two worst PMI lists with respect to each ofPRB #0 to PRB #4, and notifies the NodeB #1 of the selected lists. Inthis manner, the ICIC of the frequency domain and the spatial domain maybe realized.

However, in a case where the transmission system in Non-PatentLiterature 1 and Non-Patent Literature 2 is extended to a frequencydomain, it is necessary for the NodeB #0 to notify other nodes ofextended PMI list information for each frequency band, such that thereis a problem in that overhead increases and therefore a traffic over thebackhaul is made to be heavy. For example, in a case where a system band(20 MHz) is made up by 110 PRBs, and two PMIs are selected from sixteen(=2⁴) kinds of PMIs (codebook) for each PRB and are notified, controlinformation of 880 bits ((the number of PRBs=110)×(notified bit numbersof 1 PMI for each PRB=4 bits)×2=880 bits) is necessary for each node.Furthermore, in the LTE-advanced, review has been made with respect to atechnology called carrier aggregation (spectrum aggregation) in which aplurality of bands that are made up of 20 MHz called a component carrier(CC) are collected (made to have a wide band) and a high-speedtransmission is realized, such that in this case, the increase inoverhead becomes a further significant problem.

Therefore, an object of the invention is to provide a communicationapparatus and a communication method, which are capable of reducingoverhead related to precoding information (for example, PMI) andbeamforming weight information that are notified over a backhaul whilemaintaining an ICI reduction effect due to DL coordinated CoMP (CB, JP,or the like) among a plurality of nodes.

Solution to Problem

The present invention provides a communication apparatus including: agenerator that generates frequency resource position informationcorresponding to first information which is based on communicationquality information received from user equipments, the frequencyresource position information indicating validity or invalidity of thefirst information for each frequency resource, and a transmitter thattransmits the first information, the frequency resource positioninformation and a cell ID which the frequency resource position isapplied, to another communication apparatus via a backhaul.

The present invention also provides a communication method including:generating frequency resource position information corresponding to afirst information which is based on communication quality informationreceived from user equipments, the frequency resource positioninformation indicating validity or invalidity of the first informationfor each frequency resource, and transmitting the first information, thefrequency resource position information and a cell ID which thefrequency resource position is applied, to another communicationapparatus via a backhaul.

Advantageous Effects of Invention

According to the communication apparatus and the communication methodrelated to the invention, it is possible to reduce overhead related toinformation that is notified over a backhaul while maintaining an ICIreduction effect due to DL coordinated CoMP (CB, JP, or the like) amonga plurality of nodes.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a conceptual diagram of a transmission system according to afirst embodiment.

FIG. 2 is a block diagram illustrating a configuration of acommunication apparatus 100 in the transmission system according to thefirst embodiment.

FIG. 3 is a flowchart illustrating a control sequence in thetransmission system shown in FIG. 2.

FIG. 4 is an example of an extended PMI list according to the firstembodiment.

FIG. 5 is an example of an extended PMI list selected by an extended PMIlist selecting unit 131.

FIG. 6 is a block diagram illustrating a configuration of acommunication apparatus 100A according to a first modification exampleof the first embodiment.

FIG. 7 is an example of an extended PMI list according to the firstmodification example.

FIG. 8 is a flowchart illustrating a control sequence of a transmissionsystem according to the first modification example.

FIG. 9 is an example of an extended PMI list according to a secondmodification example of the first embodiment.

FIG. 10 is an example of an extended PMI list according to a thirdmodification example of the first embodiment.

FIG. 11 is an example of an extended PMI list according to a fourthmodification example of the first embodiment.

FIG. 12 is an example of an extended PMI list according to a fifthmodification example of the first embodiment.

FIG. 13 is a diagram illustrating an example (1) in which a sub-bandnumber and whether or not PMI notification in the same sub-band isperformed are notified with a bitmap in the first embodiment.

FIG. 14 is a diagram illustrating an example (2) in which the sub-bandnumber and whether or not PMI notification in the same sub-band isperformed are notified with a bitmap in the first embodiment.

FIG. 15 is an example of an extended PMI list according to a secondembodiment.

FIGS. 16A and 16B are examples of an extended PMI list according to athird embodiment.

FIG. 17 is a diagram illustrating a method of notifying other nodes ofan indicator of RNTP and the PMI list at the same time.

FIG. 18 is a block diagram illustrating a configuration of acommunication apparatus 600 according to a fourth embodiment.

FIG. 19 is a diagram illustrating a method (1) of notifying other nodesof the RNTP and the PMI list in such a manner that a notification timingof RNTP and a notification timing of a PMI list are shifted from eachother.

FIG. 20 is a diagram illustrating a method (2) of notifying other nodesof the RNTP and the PMI list in such a manner that the notificationtiming of RNTP and the notification timing of a PMI list are shiftedfrom each other.

FIGS. 21A and 21B are diagrams illustrating a method of transmitting twopieces of information at the same time with the specific same frequencyresource.

FIG. 22A is a conceptual diagram in a case where the indicator of theRNTP is shared between cells, and FIG. 22B is an example of theindicator of the RNTP for each PRB in a frequency domain.

FIG. 23 is a conceptual diagram of a case in which coordinatedbeamforming is performed among a plurality of cells on the basis of thePMI information.

FIG. 24 is an example of a transmission system to effectively reduceinter-cell interference coordinated (ICIC).

MODES FOR CARRYING OUT INVENTION

Hereinafter, embodiments of the invention will be described withreference to drawings.

Each of the embodiments of the invention is based on the followingviewpoints.

(1) When based on a general cell design (area development of a node) toimprove expansion of a coverage and a service quality by considering areduction in installing cost of a node and usage efficiency thereof,among UEs that are uniformly present within a cell, a proportion of UEsthat are present at a cell edge is at most substantially 10 to 20%. Inaddition, a transmission rate of the UE, which is present at the celledge in which a radio channel quality is bad (a Signal-to-Interferenceplus Noise power Ratio (SINR) is low), is significantly lower than thatof a UE that is present in the vicinity of the node. Therefore, anallocation of a frequency resource that is used by the UE that ispresent at the cell edge is at most substantially 10 to 20% within asystem band. That is, a proportion of a frequency resource that needsextended beamforming (PMI) information for CoMP is also at mostsubstantially 10 to 20% within the system band. In other words, inregard to resources of substantially 80 to 90% of the system band, it isnot necessary for the extended beamforming (PMI) information that isnecessary for the CoMP to be shared between nodes. Therefore, an amountof the extended beamforming (PMI) information is variably controlled inresponse to a resource position within the system band, which allocatesthe UE that is present at the cell edge, and is notified to other nodes.

(2) Since a main target of the coordinated beamforming between cells isUEs that are present at the cell edge, the PMI information to benotified to other nodes is sufficient only with extended PMI informationof other cells in a frequency resource to be allocated to the cell edgeUE of the serving cell. Therefore, only the coordinated PMI (beamformingweight) information in a specific resource (at minimum), which othernodes need for the ICIC, is selected and is notified to other nodes.

(3) The frequency resource to be allocated to the UE that is present atthe cell edge (or in the vicinity of the cell edge) of the serving cellis considered to be expressed by the information (for example, 1 (or 0)information of the RNTP) of the transmission signal power of the servingcell. That is, when the indicator of the RNTP is 0 (or 1), since thetransmission power is small (or large), the frequency resource may beestimated to be used by the UE that is present in the vicinity of thecell (at the edge). In other words, the frequency resource (frequencyresource that allocates the cell edge UE in the serving cell) of thecoordinated beamforming, which other cells need, may be estimated onlywith the serving node without needing notified information from othernodes. Therefore, each node may autonomously select the coordinated PMI(beamforming weight) information in the specific resource (at minimum)which other nodes need for the ICIC.

From the above-described viewpoints of (1) to (3), as one characteristicof each embodiment of the invention, each node autonomously selects(only with the serving node) only useful minimum PMI information (ofspecific frequency resource), which other nodes need for the ICIC, fromthe transmission signal power in the serving cell (in LTE Rel. 8,information (an indicator of the RNTP) of future transmission signalpower or a communication quality, and notifies other nodes of theselected information via a backhaul. In this manner, the minimum anduseful information may be shared between nodes for inter-cellcoordination in an autonomously dispersed manner while reusing a formatof Rel. 8 (that is, maintaining a backward compatibility), such that dueto optimization of the beamforming information in an entire system(among a plurality of cells), the throughput in the plurality of cellsmay be improved.

(First Embodiment)

A first embodiment will be described in detail. This embodiment has thefollowing characteristics (a) to (c).

(a) An amount of precoding (beamforming) information (for example, thenumber of PMI lists) that is to be notified to other nodes via thebackhaul is variably controlled in response to a resource position of afrequency domain, and this information and information of a selectedfrequency resource position are notified to other nodes.

(b) Information of a magnitude of future transmission power (density), amagnitude of (normalized) transmission signal energy (density), or goodor bad of a communication quality for each frequency resource in theserving cell, and the amount of the precoding (beamforming) information(for example, the number of PMI lists) at the frequency resourceposition are correlated with each other.

(c) As the future transmission power (density) or (normalized)transmission signal energy (density) for each frequency resource in theserving cell is large (or small), or as the communication qualitybecomes better (or worse) for each frequency resource in the servingcell, the amount of precoding (beamforming) information (for example,the number of PMI lists) at a corresponding resource is made to increase(or decrease).

FIG. 1 shows a conceptual diagram of a transmission system according tothe first embodiment. FIG. 2 shows a block diagram of a communicationapparatus (base station (NodeB)) 100 in the transmission systemaccording to this embodiment. In addition, FIG. 3 shows a diagramillustrating a control sequence in the transmission system shown in FIG.1.

In the transmission system shown in FIG. 1, a NodeB #0 (a serving cell)selects an amount of precoding (beamforming) information (for example,the number of worst PMI lists), which is notified to other nodes, inresponse to information of transmission signal power for each frequencyresource in the serving cell ((2)-1 in the drawing), and notifies NodeB#1 (non-serving cell) that is another node of the amount of theprecoding (beamforming) information for each frequency resource via abackhaul (for example, an X2 interface). In this manner, the NodeB #0(serving cell) performs the ICIC of a frequency domain and a spatialdomain.

In FIG. 1, as an amount of precoding (beamforming) information for eachfrequency band, a worst PMI list is shown. For example, in a physicalresource block (PRB) number of #0, since transmission signal power islarge, two worst PMI #0 and worst PMI #3 are shown in the worst PMIlist.

The communication apparatus (base station (NodeB)) 100 shown in FIG. 2includes a reception processing unit 101, a control informationextracting unit 103, an extended PMI list storing unit (for a servingnode) 105, a precoding weight determining unit 107, a data informationtransmission processing unit 109, a control information transmissionprocessing unit 111, a reference signal transmission processing unit113, a radio transmission processing unit 119, a radio receptionprocessing unit 125, a control information extracting unit 127, anextended PMI list storing unit (for other nodes) 129, an extended PMIlist selecting unit 131, a control information generating unit 133, atransmission processing unit 135, and a transmission and receptionantenna 137. Hereinafter, in this embodiment, it is assumed that thecommunication apparatus 100 is located in the NodeB #0 (serving cell).

<Operation of NodeB #0>

The NodeB #0 (serving cell) receives an extended PMI feedback requestsignal from an upper layer, and inputs this information to the controlinformation transmission processing unit 111. It is assumed that thisextended PMI (beamforming) request is notified, for example, withsignaling of a higher layer.

The control information transmission processing unit 111 converts theextended PMI feedback request signal into a binary bit sequence,performs a predetermined transmission signal processing such as channelencoding and modulation, and outputs the resultant signal to the radiotransmission processing unit 119.

In addition, the reference signal transmission processing unit 113performs a predetermined transmission signal processing according to areference signal transmitting request, and outputs the generatedreference signal to the radio transmission processing unit 119. As akind of reference signal, CRS (Cell Specific Reference Signal), CSI-RS(Channel State Information Reference Signal), DMRS (De-ModulationReference Signal), and US-RS (User Specific Reference Signal) may beexemplified.

The radio transmission processing unit 119 performs a radio transmissionprocessing such as D/A conversion, amplification, and up-conversion withrespect to a signal input from the control information transmissionprocessing unit 111, and transmits the signal subjected to the radiotransmission processing toward a UE as an extended PMI (beamforming)request signal via the transmission and reception antenna 137. Inaddition, the radio transmission processing unit 119 performs the sameprocessing with respect to a reference signal input from the referencesignal transmission processing unit 113 and transmits the processedreference signal via the transmission and reception antenna 137.

<Operation of UE>

Here, an operation of user equipment (UE) 200 that is connected to theNodeB #0 will be described. Hereinafter, the user equipment 200 issometimes simply written as a UE. In addition, in a case where aplurality of UEs, which are the items of user equipment 200, arepresent, the UEs are sometimes written as UE #0, UE #1, UE #2, and thelike for distinguishing the plurality of UEs.

The UE receives the extended PMI (beamforming) request signal for aserving UE, which is transmitted from the NodeB #0. In addition, the UEreceives a reference signal (RS) of a serving cell (serving cell) and areference signal (RS) of other cells (non-serving cells).

In addition, the UE performs channel estimation/quality measurementbetween the NodeB #0 (serving cell) and the serving UE and channelestimation/quality measurement between the NodeB #1 (non-serving cell)and the serving UE from the received reference signals (RSs) of theserving cell (serving cell) and other cells (non-serving cells), andselects an extended PMI (for example, worst PMI list) of other cells,which generates large inter-cell interference (ICI) with the serving UEor reduces a reception SINR (Signal-to-Interference plus Noise Ratio) byusing the channel estimation result/measurement result. Here, the PMI isdefined between the NodeB and the UE in advance, and it is assumed thatthe NodeB and the UE share this information.

In addition, the UE may perform channel estimation/quality measurementbetween the NodeB #0 and the serving UE, and may additionally select anoptimal PMI (for example, best PMI) between the NodeB #0 and the servingUE by using the channel estimation result/measurement result between theNodeB #0 and the serving UE. In addition, the UE may simultaneouslyidentify a cell ID of another cell, which corresponds to the selectedextended PMI, for example, from the CRS of other cells, or the like.

Next, the UE feedback-transmits the selected extended PMI (worst PMIlist) to the NodeB #0 (serving cell) as a control signal according to apredetermined transmission processing sequence such as a modulationprocessing. In addition, the UE may additionally feed back the optimalPMI (best PMI) in the serving cell. (At this time, the UE may feed backa cell ID of another cell, which corresponds to the identified extendedPMI, together with the extended PMI information. Therefore, the NodeB #0(serving cell), which is a feedback destination, may recognize whichcell (node) generates other-cell interference with which UE. Therefore,this may be used for frequency scheduling (allocation of a plurality ofUEs to a frequency resource) within the NodeB #0 (serving cell), suchthat a multi-user diversity based on the frequency resource allocationwithin the NodeB #0 (serving cell) may be improved and thereby a cellthroughput may be improved.). In addition, the optimal PMI (for example,best PMI) between the NodeB #0 and the serving UE may be additionallyselected.

The NodeB #0 receives a control signal related to the extended PMI(worst PMI list) that is transmitted from a plurality of UEs in theserving cell (and the identified cell ID corresponding to the extendedPMI) via the transmission and reception antenna 137, and inputs thecontrol signal to the radio reception processing unit 125.

The radio reception processing unit 125 performs a reception processingsuch as down-conversion and A/D conversion, and demodulates and decodesthe control signal to which the reception processing has been performed.In addition, the radio reception processing unit 125 outputs thedemodulated and decoded control signal to the control informationextracting unit 127.

The control information extracting unit 127 extracts the extended PMIinformation (and the cell ID) that are included in the control signalinput from the radio reception processing unit 125, and outputs theextracted extended PMI information to the extended PMI list storing unit(for other nodes) 129.

The extended PMI list storing unit (for other nodes) 129 generates anextended PMI list that is fed back from the plurality of UEs in theserving cell for each frequency resource (for example, in PRB units).For example, the extended PMI list storing unit 129 generates anextended PMI (worst PMI list) that is expected not to be used by othercells (whose use is restricted, prohibited, and not encouraged). Forexample, to reduce other-cell interference from the NodeB #1(non-serving cell) that is a neighbor cell of the NodeB #0 to the NodeB#0 (serving cell), the extended PMI list storing unit 129 generates anextended PMI list in frequency resource (PRB) units, in which use in theneighbor cell NodeB #1 is restricted (prohibited, and not encouraged)(refer to FIG. 4).

FIG. 4 shows an example of the extended PMI list according to the firstembodiment. The horizontal axis represents a frequency. As shown in FIG.4, for example, in a physical resource (PRB) number #0, worst PMI #0 andworst PMI #5 as a PMI fed back from the UE #0 in the serving cell andworst PMI #3 as a PMI fed back from the UE #2 in the serving cell arepresent. In addition, as shown in FIG. 4, for example, in the physicalresource (PRB) number #3, worst PMI #9 as a PMI fed back from the UE #0in the serving cell, worst PMI #0 and worst PMI #3 as a PMI fed backfrom the UE #1 in the serving cell, and worst PMI #8 as a PMI fed backfrom the UE #2 in the serving cell are present.

In addition, the extended PMI list shown in FIG. 4 may be individuallygenerated for each of other cells on the basis of the cell ID that isfed back together with the extended PMI, or may be generated with onelist by collecting a plurality of cells among other cells other than theserving cell. In the case of creating one list by collecting theplurality of cells among other cells other than the serving cell,complexity and computation of the NodeB #0 may be reduced.

In addition, the extended PMI list storing unit (for other nodes) 129outputs the generated extended PMI list to the extended PMI listselecting unit 131.

A control unit 123 determines a position of a specific frequencyresource and the number of notification PMIs (amount of precoding andbeamforming information) at the resource, which are selected as PMIinformation to be notified to other nodes via the backhaul, from atransmission mode (transmission mode of CoMP, JP/CB/CS, or the like) foreach frequency resource, position information of the UE, information ofthe transmission signal power for each frequency resource, or the like,and outputs the determined position and the determined number of PMIs tothe extended PMI list selecting unit 131 and the control informationgenerating unit 133.

The extended PMI list selecting unit 131 selects the extended PMI list(amount of precoding (beamforming) information) for each frequencyresource, which is input from the extended PMI list storing unit (forother nodes) 129, on the basis of the specific frequency resourceposition and the number of notification PMIs (amount of precoding andbeamforming information) in the resource, which are selected as the PMIinformation to be notified to other nodes via the backhaul and which areinput from the control unit 123.

Here, an example of the extended PMI list for each frequency resource,which is selected by the extended PMI list selecting unit 131, is shownin FIG. 5. As shown in FIG. 5, for example, in regard to a physicalresource block (PRB) number #0, worst PMI #5 and worst PMI #0 that arefed back from the UE #0, and worst PMI #3 that is fed back from the UE#2 are selected. In addition, in regard to PRB #3, worst PMI #9 that isfed back from the UE #0, worst PMI #8 that is fed back from the UE #2,and worst PMI #3 and worst PMI #0 that are fed back from the UE #1 areselected.

In addition, the extended PMI list selecting unit 131 outputs thenotification PMI list shown in FIG. 5, which is variably selected foreach frequency resource, to the control information generating unit 133so as to notify a node to which a corresponding cell belongs of thenotification PMI list. In addition, in the case of the example shown inFIG. 5, the extended PMI lists of the PRB number #0 and PRB #3 areoutput.

In addition, in a case where in the extended PMI list storing unit (forother nodes) 129, the extended PMI list for each frequency resource isgenerated for each cell ID, the notification extended PMI list, which isselected for each cell, is output to the control information generatingunit 133 together with the cell ID. In addition, in a case where in theextended PMI list storing unit (for other nodes) 129, the extended PMIlist for each frequency resource is generated for each cell group inwhich a plurality of cell IDs are collected, the extended PMI list isoutput to the control information generating unit 133 together with thecorresponding plurality of cell ID or a cell group ID of the group.

The control information generating unit 133 generates controlinformation by performing a process of converting the extended PMI list(and the cell ID and cell group ID) that is input from the extended PMIlist selecting unit 131 and the notification frequency resource positionthat is input from the control unit 123 into a binary sequence, or thelike, and outputs the generated control information to the transmissionprocessing unit 135. As a method of expressing the notificationfrequency resource position, for example, whether or not the extendedPMI list is present for each frequency resource may be expressed as ON(=1)/OFF (=0) of a bitmap. That is, in a frequency resource in which thePMI list to be notified is present, the position is expressed as 1 (ON),and in a frequency resource in which the PMI list to be notified is notpresent, the position is expressed as 0 (OFF). In FIG. 5, since the PMIlist to be notified is present in the positions of frequency resourcesof PRB #0 and PRB #3, the positions are expressed as 1, and since thePMI list to be notified is not present in the other positions (PRB #1,PRB #2, and PRB #4) of the frequency resources, the positions areexpressed as 0.

After adding a header representing a destination address of atransmission node (cell), or the like with respect to the extended PMIlist (and cell ID and group cell ID) and the notification frequencyresource number that are input with reference to the information of thecell ID (or the group cell ID), the transmission processing unit 135performs a predetermined processing to generate a transmission signalover the backhaul and transmits this signal to other nodes (cells).

The reception processing unit 101 receives control information relatedto the extended PMI list (and the cell ID and group cell ID) and thenotification frequency resource number that are transmitted from othernodes (cells), performs a predetermined processing such as confirmationof the destination address or the like, and then outputs the controlinformation to the control information extracting unit 103.

The control information extracting unit 103 extracts the extended PMIlist (and the cell ID and group cell ID) and the notification frequencyresource number, which are included in the control signal and aretransmitted from other nodes (cells), and outputs them to the extendedPMI list storing unit (for a serving node) 105.

The extended PMI list storing unit (for a serving node) 105 generatesthe extended PMI list for each of other cells or for each cell group,and for each frequency resource, and outputs this information to theprecoding weight determining unit 107.

The precoding weight determining unit 107 determines, for example, aprecoding weight for each frequency resource that maximizes the cellthroughput or a precoding weight for each UE within a serving cell onthe basis of the best PMI feedback information for each frequencyresource, which is input from the UE of the serving cell, the extendedPMI list (for example, worst PMI list) for each frequency resource ofother cells (or for each cell group), which is input from the extendedPMI list storing unit (for a serving node) 105, or the like. Inaddition, the determined weight information is output to the datainformation transmission processing unit 109, the control informationtransmission processing unit 111, or the reference signal transmissionprocessing unit 113.

The data information transmission processing unit 109 performs apredetermined processing such as channel encoding and modulation withrespect to the input data signal for the UE, and then performs precodingwith respect to a transmission data signal on the basis of the weightinformation input from the precoding weight determining unit 107. Then,the data information transmission processing unit 109 outputs thepre-coded data signal to the radio transmission processing unit 119.

In addition, the control information transmission processing unit 111and the reference signal transmission processing unit 113 may performprecoding with respect to a control signal and a reference signal(particularly, DMRS) on the basis of the precoding weight informationinput from the precoding weight determining unit 107.

Here, a control sequence in the transmission system shown in FIG. 1 willbe described with reference to FIG. 3. FIG. 3 shows a diagramillustrating a control sequence in the transmission system shown in FIG.1.

In step ST31, the NodeB #0 (serving cell) transmits an extended PMI(beamforming) request signal toward a UE.

In steps ST32 and ST33, the UE receives a reference signal of the NodeB#0 that is a serving cell, and a reference signal of the NodeB #1(non-serving cell) that is another cell.

In step ST34, the UE feedback-transmits the extended PMI information(corresponding cell ID and optimal PMI) to the NodeB #0 as a controlsignal.

In step ST35, the NodeB #0 receives the PMI information from other UEsthat are connected to the serving cell.

In step ST36, the NodeB #0 selects and generates PMI information foreach frequency band in response to a CoMP mode for each frequency bandof the serving cell, position information of the UE, transmission signalpower information, or the like.

In step ST37, the NodeB #0 notifies the NodeB #1 of the PMI informationand information of the selected frequency band position.

In step ST38, the NodeB #0 notifies other NodeBs of the PMI informationand the information of the selected frequency band position.

As described above, according to the transmission system related to thisembodiment, the communication apparatus 100 autonomously selects andnotifies only necessary minimum precoding (beamforming) information ofthe UE that performs the CoMP among the plurality of cells in a specificfrequency resource in response to the transmission signal powerinformation or the like, such that it is possible to reduce overheadrelated to precoding (beamforming weight (for example, the number of PMIlists)) information that is notified over the backhaul while maintainingthe ICI reduction effect due to DL coordinated CoMP (CB, JP, or thelike) among a plurality of nodes.

In addition, according to the transmission system related to thisembodiment, since the communication apparatus 100 performs notificationof only the precoding (beamforming) information with respect to a UEthat is present at the cell edge, the overhead is reduced, and thedegree of freedom of the scheduling in a frequency domain and a spatialdomain among a plurality of cells, that is, a multi-user diversityeffect among the plurality of cells, which are based on the allocationof the UE with respect to the frequency resource and the spatialresource among the plurality of cells, may be also maintained.

Here, an effect of the transmission system related to this embodimentwill be described with respect to, for example, a case of the followingthree conditions.

(1) All of UEs, which are present at the cell edge in a proportion ofsubstantially 10% within the cell, perform the CoMP, and the UEs occupythe frequency resource of substantially 10% of the system band.

(2) One PMI is expressed with 4 bits, and the number of notificationPMIs for each PRB are two.

(3) The position information of the frequency resource at which the PMIis notified is expressed as a bitmap using 110 bytes. For example, theposition information is notified in a state in which the frequencyresource at which the PMI is notified is defined to indicate 1 and thefrequency resource at which the PMI is not notified is defined toindicate 0.

In the case of the above-described conditions of (1) to (3), in thetransmission system according to this embodiment, the number of totalbits of the PMI to be notified to other nodes and the frequency resourceposition information of the selected PMI is 198 bits, which is the sumof 88 bits (=(110×0.1)×4×2)) that is the number of total notificationbits of the PMI and 110 bits that is the number of bits of the frequencyresource position information of the selected PMI. Therefore, it can beunderstood that the overhead may be greatly reduced compared to thetechnology in which a transmission system in Non-Patent Literature 1 andNon-Patent Literature 2 is extended to the frequency domain that wasillustrated with reference to FIG. 24.

That is, when using a viewpoint in which a proportion of the number ofUEs that are objects of the CoMP is greatly smaller than the number oftotal UEs (or, the number of UEs that are not objects of the CoMP) inthe cell, even when “the frequency resource position information of theselected PMI” is notified in addition to “the selected PMI information”,the total overhead may be greatly reduced compared to the technology inwhich the transmission system in Non-Patent Literature 1 and Non-PatentLiterature 2 is extended to the frequency domain (method in which onlythe PMI information in the total frequency resources is notified), whichwas described with reference to FIG. 24.

[First Modification Example]

In a first modification example according to the first embodiment, acommunication apparatus 100A is characterized in that information of amagnitude of transmission power (density) or (normalized) transmissionsignal energy (density), or information of good or bad of acommunication quality for each frequency resource in the serving cell,and an amount of precoding (beamforming) information (for example, thenumber of PMI lists) at the frequency resource position are correlatedwith each other. In addition, the conceptual diagram of the transmissionsystem according to the first embodiment shown in FIG. 1 may be alsoapplied to this modification example.

FIG. 6 shows a block diagram illustrating a configuration of thecommunication apparatus 100A according to the first modificationexample.

The communication apparatus (base station (NodeB)) 100A shown in FIG. 6includes a reception processing unit 101, a control informationextracting unit 103, an extended PMI list storing unit (for a servingnode) 105, a precoding weight determining unit 107, a data informationtransmission processing unit 109, a control information transmissionprocessing unit 111, a reference signal transmission processing unit113, a scheduler unit 115, a transmission signal power control unit 117,a radio transmission processing unit 119, a unit 121 that generates atransmission power (RNTP) indicator for each frequency resource, acontrol unit 123, a radio reception processing unit 125, a controlinformation extracting unit 127, an extended PMI list storing unit (forother nodes) 129, an extended PMI list selecting unit 131, a controlinformation generating unit 133, a transmission processing unit 135, anda transmission and reception antenna 137. Hereinafter, in thisembodiment, it is assumed that the communication apparatus 100A islocated in the NodeB #0 (serving cell).

The communication apparatus 100A shown in FIG. 6 is different from thecommunication apparatus 100 shown in FIG. 2 in that the scheduler unit115, the transmission signal power control unit 117, and the indicatorgenerating unit 121 are provided. Hereinafter, the same referencenumbers are given to the same components as the communication apparatus100 shown in FIG. 2, and a detailed description thereof will not berepeated.

The scheduler unit 115 determines a frequency resource allocation of aUE in a serving cell and a transmission signal power value for eachfrequency resource on the basis of QoS (Quality of Service) that isinput or CQI (Channel Quality Indicator) that is fed back from a UE. Inaddition, the scheduler unit 115 outputs this information to thetransmission signal power control unit 117.

The transmission signal power control unit 117 generates a controlsignal to control an amplifier in the radio transmission processing unit119 on the basis of the transmission signal power value for each inputfrequency resource, and outputs the control signal to the radiotransmission processing unit 119 and the RNTP indicator generating unit121.

The RNTP indicator generating unit 121 generates information (RNTPindicator) about a magnitude of a future (for example, after 1 frame)transmission signal power on the basis of the control signal and athreshold value of the RNTP that are input from the transmission signalpower control unit 117, and outputs the generated information to thecontrol unit 123.

The control unit 123 compares the extended PMI list that is generatedfor each frequency resource input from the extended PMI list storingunit (for other nodes) 129, and the information of the magnitude of thetransmission signal power (density) (information of RNTP indicator) foreach frequency resource in the serving cell or the like in correlationwith each other. In addition, the control unit 123 selects the extendedPMI list of the frequency resource on the basis of the information ofthe magnitude of the transmission signal power (density) (information ofRNTP indicator) for each frequency resource.

FIG. 7 shows an example of the extended PMI list in the firstmodification example. In FIG. 7, the information of the magnitude of the(future) transmission signal power for each frequency resource iscorrelated with the extended PMI (worst PMI) list that is selected bythe control unit 123. As shown in FIG. 7, since a UE that is present ata cell edge is to be allocated to physical resource block (PRB) numbersof #0 and #3 in the future (for example, after one frame), thetransmission signal power of the frequency resource is set to be high.Therefore, the number of the frequency resource position is output tothe extended PMI list selecting unit 131.

The extended PMI list selecting unit 131 selects the extended PMI list(in the case of extended PMI list shown in FIG. 7, extended PMI lists ofPRB number #0 and PRB number #3) of the frequency resource position,which is notified from the control unit 123, and outputs the selectedextended PMI list to the control information generating unit 133. Asdescribed above, the information of the selected frequency resourceposition (for example, a bit sequence (bitmap) representing frequencyresource position at which the PMI is notified, which is shown in FIG.5) may be also output to the control information generating unit 133.

The control information generating unit 133 generates controlinformation by performing a process of converting the extended PMI list(and the cell ID and group cell ID) input from the extended PMI listselecting unit 131 and the notification frequency resource number thatis input from the control unit 123 into a binary sequence, or the like,and outputs the generated control information to the transmissionprocessing unit 135.

After adding a header representing a destination address of atransmission node (cell) or the like with respect to the extended PMIlist (and cell ID and group cell ID) and the notification frequencyresource number that are input with reference to the information of thecell ID, the transmission processing unit 135 performs a predeterminedprocessing to generate a transmission signal over the backhaul andtransmits this signal to other nodes (cells).

The reception processing unit 101 receives control information relatedto the extended PMI list (and the cell ID and group cell ID) and thenotification frequency resource number that are transmitted from othernodes (cells), performs a predetermined processing such as confirmationof the destination address or the like, and then outputs the controlinformation to the control information extracting unit 103.

The control information extracting unit 103 extracts the extended PMIlist (and the cell ID and group cell ID) and the notification frequencyresource number that are included in the control signal and aretransmitted from other nodes (cells), and outputs them to the extendedPMI list storing unit (for a serving node) 105.

The extended PMI list storing unit (for a serving node) 105 generatesthe extended PMI list for each of other cells or for each cell group,and for each frequency resource, and outputs this information to theprecoding weight determining unit 107.

The precoding weight determining unit 107 determines, for example, aprecoding weight for each frequency resource that maximizes the cellthroughput or a precoding weight for each UE within a serving cell onthe basis of the best PMI feedback information for each frequencyresource, which is input from the UE of the serving cell, the extendedPMI list for each frequency resource of other cells (or for each cellgroup), which is input from the extended PMI list storing unit (for aserving node) 105. In addition, the determined weight information isoutput to the data information transmission processing unit 109, thecontrol information transmission processing unit 111, or the referencesignal transmission processing unit 113.

The data information transmission processing unit 109 performs apredetermined processing such as channel encoding and modulation withrespect to the input data signal for the UE, and then performs precodingwith respect to a transmission data signal on the basis of the weightinformation input from the precoding weight determining unit 107. Then,the data information transmission processing unit 109 outputs thepre-coded data signal to the radio transmission processing unit 119.

In addition, the control information transmission processing unit 111and the reference signal transmission processing unit 113 may performprecoding with respect to a control signal and a reference signal(particularly, DMRS) on the basis of the precoding weight informationinput from the precoding weight determining unit 107.

A flow illustrating a control sequence of the transmission systemaccording to the first modification example will be described withreference to FIG. 8. FIG. 8 shows a flowchart illustrating a controlsequence of the transmission system according to the first modificationexample.

In step ST81, the NodeB #0 (serving cell) transmits an extended PMI(beamforming) request signal toward a UE.

In steps ST82 and ST83, the UE receives a reference signal of the NodeB#0 that is a serving cell, and a reference signal of the NodeB #1(non-serving cell) that is another cell.

In step ST84, the UE feedback-transmits the PMI information to the NodeB#0 as a control signal.

In step ST85, the NodeB #0 receives the PMI information from other UEsthat are connected to the serving cell.

In step ST86, the NodeB #0 generates and selects the PMI information inresponse to information of the transmission power (density),(normalized) transmission signal energy (density), or a magnitude (goodor bad) of a communication quality for each frequency resource in theserving cell.

In step ST87, the NodeB #0 notifies the NodeB #1 of the PMI informationand information of the selected frequency band position.

In step ST88, the NodeB #0 notifies other NodeBs of the PMI informationand the information of the selected frequency band position.

As described above, according to the transmission system related to thefirst modification example, the communication apparatus 100A mayautonomously select precoding (beamforming) information in a specificresource, which other nodes need for the ICIC, only with the servingnode on the basis of information (for example, an RNTP indicator) aboutthe magnitude of future transmission signal power in the serving cell,such that overhead related to the PMI (beamforming weight (for example,the number of PMI lists information) that is notified over the backhaulmay be reduced.

In addition, in addition to the future transmission power (density)information for each frequency resource in the serving cell, thecommunication apparatus 100A may correlate information of the(normalized) transmission signal energy (density) or the magnitude (goodor bad) of the communication quality (CQI), or the like, and the amountof precoding (beamforming) information (for example, the number of PMIlists) at the frequency resource position with each other. Therefore,the same effect as that obtained by the transmission system related tothe above-described first modification example may be obtained.

In addition, in a case where the communication apparatus 100A notifiesother nodes of the future transmission power (density) information, the(normalized) transmission signal energy (density), or the magnitude(good or bad) of the communication quality (CQI) for each frequencyresource together with each other, the information of the selectedfrequency resource position may not be notified. When theabove-described correlation rule is shared between coordination nodes,for example, since the frequency resource at which the PMI is notifiedmay be specified from the notified transmission power information foreach frequency resource, even when the position information of theselected frequency resource is not notified, the same effect as thatobtained by the transmission system related to the first modificationexample may be obtained.

[Second Modification Example]

As the transmission power (density) or (normalized) transmission signalenergy (density) for each frequency resource in the serving cell islarge (or small), or as the communication quality becomes better (orworse) for each frequency resource in the serving cell, a communicationapparatus of a second modification example related to the firstembodiment allows the extended PMI list selecting unit 131 to increase(or decrease) the amount of the precoding (beamforming) information (forexample, the number of PMI lists) at a corresponding resource.

Here, an operation of the communication apparatus of the secondmodification example related to the first embodiment is different fromthe operation of the communication apparatus 100A in an operation of theextended PMI list selecting unit 131, and therefore, in thismodification example, the operation of the extended PMI list selectingunit 131 that performs the different operation will be mainly described.

The operation of the extended PMI list selecting unit 131 in thetransmission system related to the second modification example will bedescribed with reference to FIG. 9. FIG. 9 shows an example of theextended PMI list in the second modification example. In FIG. 9, thetransmission power (density) for each frequency resource is also shownin the extended PMI list. In the extended PMI list shown in FIG. 9, thenumber of extended PMI lists at a frequency resource varies in responseto the magnitude of the transmission signal power for each frequencyresource.

As shown in FIG. 9, the extended PMI list selecting unit 131 sets twothreshold values (a transmission signal power threshold value 1 and atransmission signal power threshold value 2) to the transmission signalpower, and defines the magnitude of the transmission signal power inthree regions (“large”, “middle”, and “small”). At this time, (1) whenthe value of the transmission signal power is in the “small” region, thenumber of extended PMI lists to be notified is set to 0, (2) when thevalue of the transmission signal power is in the “middle” region, thenumber of PMI lists to be notified is set to 1, and (3) when the valueof the transmission signal power is in the “large” region, the number ofextended PMI lists to be notified is set to 2,

In addition, the extended PMI list selecting unit 131 selects theextended PMI for each frequency resource, that is, for PRB numbers of #0to #7 on the basis of the number of extended PMI lists depending on themagnitude of the transmission signal power.

For example, as shown in FIG. 9, at PRB #1, since the value of thetransmission signal power is in the “large” region, the number ofextended PMI lists to be notified becomes 2. Therefore, at PRB #1, twoextended PMIs of extended PMI #1 and extended PMI #0 are selected. Inaddition, at PRB #4, since the value of the transmission signal power isin the “small” region, the number of extended PMI lists to be notifiedbecomes 0. Therefore, at PRB #4, the extended PMI is not selected in theextended PMI list shown in FIG. 9.

As described above, in the transmission system related to the secondmodification example, the larger (or smaller) the transmission signalpower for each frequency resource, the further the extended PMI listselecting unit 131 increases (or decreases) the amount of the precoding(beamforming) information (for example, the number of PMI lists) at thisresource.

Therefore, in regard to the transmission system related to the secondmodification example, the communication apparatus of the secondmodification example related to the first embodiment increasescoordination CB/JP information only in a specific frequency resource inwhich large interference may be applied to other cells with highprobability when seen from the serving node (large interference fromother cells when seen from other nodes), such that the ICI reductioneffect due to the coordination ICIC among a plurality of nodes may befurther improved.

In addition, in regard to the transmission system related to the secondmodification example, the communication apparatus of the secondmodification example related to the first embodiment may performcorrelation with respect to the amount of the beamforming information ina corresponding band on the basis of the transmission signal powerdensity and the (normalized) transmission signal energy (density) inaddition to the transmission signal power for each frequency resource.For example, the larger (or smaller) the transmission signal powerdensity, the (normalized) transmission signal energy (density), thefurther the amount of the precoding (beamforming) information (forexample, the number of PMI lists) at a corresponding resource may beincreased (or decreased). Therefore, the same effect as described abovemay be obtained.

In addition, in regard to the transmission system related to the secondmodification example, the communication apparatus of the secondmodification example related to the first embodiment may correlatecommunication quality (CQI (Channel Quality)) information (SIR(Signal-to-Interference Ratio), SINR (Signal-to-Interference plus NoiseRatio), or the like) that is fed back from a UE, and the amount of thebeamforming information at a corresponding band with each other. Inaddition, the communication apparatus may correlate measurementinformation (RSRP, RSRQ, RSSI, or the like) that is fed back from a UE,and the amount of the beamforming information at a corresponding bandwith each other. For example, the larger (or smaller) the communicationquality (CQI (Channel Quality)), RSRP, RSRQ, or the like), the furtherthe amount of the precoding (beamforming) information (for example, thenumber of PMI lists) may be increased (or decreased) at a correspondingresource. Therefore, even when a UE, which needs a high-speed rate(needs high CQI (SINR)), other than a UE that is present at a cell edgeis allocated to the frequency resource, inter-cell interference withrespect to the UE may be reduced.

[Third Modification Example]

A communication apparatus of a third modification example related to thefirst embodiment allows the extended PMI list selecting unit 131 tocorrelate a binary indicator (information representing futuretransmission signal power) of the RNTP for each physical resource block(PRB), and an amount of the precoding (beamforming) information (forexample, the number of PMI lists) of a corresponding band with eachother.

Here, an operation of the communication apparatus of the thirdmodification example related to the first embodiment is different fromthe operation of the communication apparatus 100A in an operation of theextended PMI list selecting unit 131, and therefore, in thismodification example, the operation of the extended PMI list selectingunit 131 that performs the different operation will be mainly described.

In DL transmission of LTE Rel. 8, RNTP (Relative Narrowband TX Power),which is an index representing information of future transmission signalpower (normalized EPRE (Energy Per Resource Element)) in physicalresource block (PRB) units, is defined as a binary indicator (0 or 1).In this modification example, an index, which is used in the DLtransmission of LTE Rel. 8, is used. That is, the communicationapparatus of the third modification related to the first embodimentreuses a format defined in LTE Rel. 8, that is, may maintain backwardcompatibility.

Here, in regard to the transmission system related to the thirdmodification example, the operation of the extended PMI list selectingunit 131 will be described with reference to FIG. 10. FIG. 10 shows anexample of the extended PMI list according to the third modificationexample. In FIG. 10, the binary indicator of the RNTP for each frequencyresource (for each of PRBs #0 to #7), which corresponds to the extendedPMI list, is also shown. The horizontal axis represents a frequency.

As shown in FIG. 10, the extended PMI list selecting unit 131 sets athreshold value of the RNTP, and (1) in a case where a value of the RNTPis less than the threshold value of the RNTP, the binary indicator ofthe RNTP is set to 0, and (2) in a case where a value of the RNTP islarger than the threshold value of the RNTP, the binary indicator of theRNTP is set to 1. In addition, (1) in a case where the binary indicatorof the RNTP is 1, the number of PMI lists to be notified is set to 2,and (2) in a case where the binary indicator of the RNTP is 0, thenumber of PMI lists to be notified is set to 1. That is, the number ofPMI lists in each of the PRBs #0 to #7 varies in response to the binaryindicator of 0 or 1 of the RNTP for each frequency resource.

For example, in the extended PMI list shown in FIG. 10, since the binaryindicator of the RNTP is 0 at PRB #0, the number of PMI lists to benotified is 1. Therefore, at PRB #0, the extended PMI list selectingunit 131 sets the number of the PMI lists to be notified to 1, andselects PMI #0. In addition, in regard to the extended PMI list shown inFIG. 10, since the binary indicator of the RNTP is 1 at PRB #3, thenumber of PMI lists to be notified is 2. Therefore, at PRB #3, theextended PMI list selecting unit 131 sets the number of PMI lists to benotified to 2, and selects PMI #2 and PMI #4.

That is, in regard to the transmission system related to the thirdmodification example, the communication apparatus of the thirdmodification example related to the first embodiment changes (increasesor decreases) the amount of the precoding (beamforming) information (forexample, the number of PMI lists) at a corresponding frequency resourcein response to the value (1 or 0) of the binary indicator of the RNTPfor each frequency resource. That is, the communication apparatus of thethird modification example related to the first embodiment variablycontrols the number of PMIs in a frequency domain.

Therefore, in regard to the transmission system related to the thirdmodification example, since the communication apparatus of the thirdmodification example related to the first embodiment correlates theindicator of the RNTP and the amount of the precoding (beamforming)information (for example, the number of PMI lists) with each other, andthereby may reuse a format defined by LTE Rel. 8, that is, may maintainbackward compatibility, the number of test items and the number ofprocesses, which are requisite (new) in practical use, may be reduced.

[Fourth Modification Example]

In regard to a transmission system of a fourth modification examplerelated to the first embodiment, a communication apparatus of the fourthmodification example related to the first embodiment allows the extendedPMI list selecting unit 131 to select a PMI list of a physical resourceblock (PRB) in which the value of the binary indicator of the RNTP foreach frequency resource is 1 and notifies other nodes of correspondingprecoding (beamforming) information via the backhaul.

In addition, in regard to this modification example, the communicationapparatus of fourth modification example related to the first embodimentmay not notify or select the precoding (beamforming) information of thePRB in which the value of the binary indicator of the RNTP for eachfrequency resource is 0.

Here, the operation of the communication apparatus of the fourthmodification example related to the first embodiment is different fromthe operation of the communication apparatus 100A in an operation of theextended PMI list selecting unit 131, and in this modification example,the operation of the extended PMI list selecting unit 131 that performsa different operation will be mainly described.

In regard to the transmission system related to the fourth modificationexample, the operation of the extended PMI list selecting unit 131 willbe described with reference to FIG. 11. FIG. 11 shows an example of theextended PMI list according to the fourth modification example. In FIG.11, the binary indicator of the RNTP for each frequency resource (foreach of PRBs #0 to #7), which corresponds to the extended PMI list, isalso shown.

As shown in FIG. 11, the extended PMI list selecting unit 131 sets athreshold value of the RNTP, and (1) in a case where a value of the RNTPis less than the threshold value of the RNTP, the binary indicator ofthe RNTP is set to 0, and (2) in a case where a value of the RNTP islarger than the threshold value of the RNTP, the binary indicator of theRNTP is set to 1. In addition, (1) in a case where the binary indicatorof the RNTP is 1, the number of PMI lists to be notified is set to 2,and (2) in a case where the binary indicator of the RNTP is 0, thenumber of PMI lists to be notified is set to 0. That is, the number ofPMI lists in each of the PRBs #0 to #7 varies in response to the binaryindicator of 0 or 1 of the RNTP for each frequency resource. Inaddition, in an example of this modification example, in a case wherethe binary indicator of the RNTP is 0, the PMI list to be notified isnot present.

For example, in the extended PMI list shown in FIG. 11, since the binaryindicator of the RNTP is 0 at PRB #0, the number of PMI lists to benotified is 0. Therefore, at PRB #0, the extended PMI list selectingunit 131 does not select the PMI lists to be notified. In addition, inregard to the extended PMI list shown in FIG. 11, since the binaryindicator of the RNTP is 1 at PRB #2, the number of PMI lists to benotified is 2. Therefore, at PRB #2, the extended PMI list selectingunit 131 sets the number of PMI lists to be notified to 2, and selectsPMI #1 and PMI #2.

That is, in regard to the transmission system related to the fourthmodification example, the communication apparatus of the fourthmodification example related to the first embodiment may further reducethe overhead related to precoding (beamforming weight (for example, thenumber of PMI lists)) information to be notified over the backhaul whilemaintaining the ICI reduction effect due to the coordinated CB among aplurality of nodes.

[Fifth Modification Example]

In regard to a transmission system related to a fifth modificationexample of the first modification, in a case where the indicator of theRNTP for each frequency resource (for example, PRB) is expressed bythree values or more, the larger (or smaller) transmission signal powervalue shown by the multi-value indicator of the RNTP, the further acommunication apparatus of the fifth modification example related to thefirst embodiment decreases (or increases) the amount of the precoding(beamforming) information (for example, the number of PMI lists) at acorresponding band.

Here, the operation of the communication apparatus of the fifthmodification example related to the first embodiment is different fromthe operation of the communication apparatus 100A in an operation of theextended PMI list selecting unit 131, and in this modification example,the operation of the extended PMI list selecting unit 131 that performsa different operation will be mainly described.

In regard to the transmission system related to the fifth modificationexample, the operation of the extended PMI list selecting unit 131 willbe described with reference to FIG. 12. FIG. 12 shows an example of theextended PMI list according to the fifth modification example. In FIG.12, the ternary indicator of the RNTP for each frequency resource (foreach of PRBs #0 to #7), which corresponds to the extended PMI list, isalso shown.

As shown in FIG. 12, correlation of three regions (“large”, “middle”,and “small”) representing the magnitude of the transmission signal poweris made in response to the ternary indicator value (“10”, “01”, and“00”) of the RNTP. The three regions (“large”, “middle”, and “small”)representing the magnitude of the transmission signal power arediscriminated by setting two threshold values (transmission signal powerthreshold value 1 and transmission signal power threshold value 2) tothe transmission power. That is, the value “10” of the ternary indicatorof the RNTP corresponds to the region “large” representing the magnitudeof the transmission signal power. The value “01” of the ternaryindicator of the RNTP corresponds to the region “middle” representingthe magnitude of the transmission signal power. The value “00” of theternary indicator of the RNTP corresponds to the region “small”representing the magnitude of the transmission signal power.

In addition, in FIG. 12, (1) in a case where the value of the ternaryindicator of the RNTP is “00”, the number of PMI lists to be notified isset to 0, (2) in a case where the value of the ternary indicator of theRNTP is “01”, the number of PMI lists to be notified is set to 1, and(3) in a case where the value of the ternary indicator of the RNTP is“10”, the number of PMI lists to be notified is set to 2. That is, thelarger the value of the transmission signal power of the region is, thelarger the value of the ternary indicator of the RNTP is. Conversely,the smaller the value of the transmission signal power of the region is,the smaller the value of the ternary indicator of the RNTP is.

As shown in FIG. 12, for example, at PRB #0, the value of thetransmission signal power is present in a region to which the value “01”of the ternary indicator of the RNTP is applied and in which the valueof the transmission signal power is “middle”. Therefore, the number ofextended PMI lists to be notified becomes 1. Therefore, like theextended PMI list shown in FIG. 12, at PRB #0, the extended PMI listselecting unit 131 selects one extended PMI (extended PMI #1).

In addition, as shown in FIG. 12, for example, at PRB #1, the value ofthe transmission signal power is present in a region to which the value“10” of the ternary indicator of the RNTP is applied and in which thevalue of the transmission signal power is “large”. Therefore, the numberof extended PMI lists to be notified becomes 2. Therefore, like theextended PMI list shown in FIG. 12, at PRB #1, the extended PMI listselecting unit 131 selects two extended PMIs (extended PMI #0 andextended PMI #1).

In addition, as shown in FIG. 12, for example, at PRB #4, the value ofthe transmission signal power is present in a region to which the value“00” of the ternary indicator of the RNTP is applied and in which thevalue of the transmission signal power is “small”. Therefore, the numberof extended PMI lists to be notified becomes 0. Therefore, like theextended PMI list shown in FIG. 12, at PRB #4, the extended PMI listselecting unit 131 does not select extended PMI.

That is, in regard to the transmission system related to the fifthmodification example, in a case where the indicator of the RNTP for eachfrequency resource (for example, PRB) is expressed by three values ormore, the larger (or smaller) transmission signal power value shown bythe multi-value indicator of the RNTP, the further a communicationapparatus of the fifth modification example related the first embodimentincreases (decreases) the amount of the precoding (beamforming)information (for example, the number of PMI lists) in a correspondingband. Therefore, in regard to the transmission system related to thefifth modification example, the communication apparatus of the fifthmodification example related to the first embodiment may effectivelysuppress interference (ICI) using ICIC with a priority give to afrequency resource in which large interference (ICI) may be applied toother cells with high probability. In addition, an appropriate amount ofPMI information, which accurately reflects the magnitude of other-cellinterference for each frequency resource, may be notified.

In addition, in the fifth modification example, the multi-valueindicator of the RNTP may be notified together with the PMI information.Therefore, effective beamforming may be performed by using two of themagnitude of the transmission power of other cells (interference powerwhen seen from the serving cell) in a frequency domain and the precodinginformation in a spatial domain.

In addition, in the transmission system according to the firstembodiment and the modification examples 1 to 5, in a case where the CBis performed as the ICIC, the communication apparatus may performnotification of precoding (beamforming) information (for example, PMIlist) that suppresses (or prohibits or restrains) the use in neighborcells as the precoding (beamforming) information (for example, PMI list)to be notified to other nodes.

In addition, in the transmission system according to the firstembodiment and the modification examples 1 to 5, in a case where the JPis performed as the ICIC, the communication apparatus may performnotification of precoding (beamforming) information (for example, PMIlist) that encourages (preferential) use in neighbor cells as theprecoding (beamforming) information (for example, PMI list) to benotified to other nodes.

In addition, in the transmission system according to the firstembodiment and the modification examples 1 to 5, the communicationapparatus may perform notification of a transmission mode thatrepresents the CB or JP together with the precoding (beamforming)information (for example, PMI list).

In this manner, to reduce other-cell interference, the coordinatedbeamforming (CB) sets the precoding (beamforming) information, which isexpected not to be used by other cells (whose use is suppressed,prohibited, and restricted), as useful information. On the other hand,to reduce other-cell interference, the joint-processing (JP) set theprecoding (beamforming) information, which is encouraged to be used byother cells, as useful information. Therefore, in each of the CS, CB,and JP, appropriate precoding (beamforming) may be performed betweencoordinated cells.

In addition, in the transmission system according to the firstembodiment and the modification examples 1 to 5, in a case wherefrequency resources at which the PMI is notified are present insuccession, an initiation number and a termination number of thefrequency resources may be notified as frequency resource positioninformation of the selected PMI. For example, in regard to a case wherethe frequency resources are made up of 110 PRBs (a case where PRBnumbers of 0 to 109 are expressed with 7 bits), when the PRB numbers atwhich the PMI is notified are 5 to 15, “initiation number=0000101 (=5)”and “termination number=0001111 (=15)” may be notified.

In addition, in the transmission system according to the firstembodiment and the modification examples 1 to 5, in a case wherefrequency resources at which the PMI is notified are present insuccession, an initiation number (or a termination number) of thefrequency resource as frequency resource position information of theselected PMI and an absolute value of a length (a bandwidth) of thesuccessive frequency resources may be notified. For example, in regardto a case where the frequency resources are made up of 110 PRBs (a casewhere PRB numbers of 0 to 109 are expressed with 7 bits), when the PRBnumbers at which the PMI is notified are 5 to 15, “initiationnumber=0000101 (=5)” (“termination number=0001111 (=15)”) and“length=0001010 (=10)” may be notified. In addition, in a case where thefrequency resource initiation number (termination number) and the lengthare notified, the notified node may acquire the termination number(initiation number) by adding the length to the initiation number (bysubtracting the length from the termination number). In addition, anidentifier (flag), which indicates the notification of the initiationnumber or the termination number, may be transmitted in addition to theabsolute value of the length (bandwidth) of the frequency resource.

In regard to the transmission system according to the first embodimentand the modification examples 1 to 5, the communication apparatus 100may further reduce the overhead related to the position information ofthe frequency resource at which the PMI is notified while maintainingthe ICI reduction effect due to the above-described two notificationmethods.

(Reduction of Frequency Resource Position Information)

In addition, in regard to the transmission system related to the firstembodiment, description was made with respect to a case in which thecommunication apparatus 100 expresses the frequency resource positioninformation of the selected PMI with a bitmap of a frequency resource,which indicates the entirety of the system band, and the entiretyinformation is notified, but it is not limited thereto. For example, inregard to the transmission system related to the first embodiment, sincethe communication apparatus 100 uses a viewpoint in which a proportionof the number of UEs that are objects of the CoMP is greatly smallerthan the number of total UEs in a cell (the number of UEs that are notobjects of the CoMP), frequency resource position information of theselected PMI may be notified with methods described below.

That is, in regard to the transmission system related to the firstembodiment, the communication apparatus 100 may define a plurality ofsub-bands by dividing the system band, may indicate the resource of thePMI notification only in the sub-band with a bitmap, and may notifyother nodes of a sub-band number and the frequency resource position inthe sub-band with a bitmap.

Therefore, a description will be made with respect to an example inwhich the sub-band number and whether or not the PMI notification in thesub-band is performed is notified with a bitmap with reference to FIG.13. FIG. 13 shows a diagram illustrating an example (1) in which asub-band number and whether or not PMI notification in the sub-band isperformed are notified with a bitmap.

As shown in FIG. 13, in regard to the transmission system related to thefirst embodiment, the system band is equally divided into four and foursub-bands are defined. That is, a sub-band #0 is correlated with asub-band number (00). A sub-band #1 is correlated with a sub-band number(01). A sub-band #2 is correlated with a sub-band number (10). Asub-band #3 is correlated with a sub-band number (11).

In addition, as shown in FIG. 13, it is assumed that in each sub-band,four physical resource blocks are present. That is, in the sub-band #0,four physical resource blocks PRB #0 to PRB #3 are present. In thesub-band #1, four physical resource blocks PRB #4 to PRB #7 are present.In the sub-band #2, four physical resource blocks PRB #8 to PRB #11 arepresent. In the sub-band #3, four physical resource blocks PRB #12 toPRB #15 are present.

In addition, in the system band shown in FIG. 13, only three physicalresource blocks PRB #5, PRB #6, and PRB #7, which are included in thesub-band #1 with which the sub-band number (01) is correlated, areselected as a PMI to be notified to other nodes.

That is, in regard to the transmission system related to the firstembodiment, the communication apparatus 100 selects the PMI to benotified to other nodes only in the sub-band #1 with which the sub-bandnumber (01) is correlated. In this case, a bit sequence that representsthe frequency resource position of the PMI to be notified to other nodesis made up of “sub-band number” and “whether or not the PMI notificationin the sub-band is performed (bitmap)”. That is, as a bit sequence inwhich the sub-band number (01) that corresponds to the sub-band #1, anda bitmap (0111), which represents whether or not the PMI notification inthe sub-band is performed, are combined, (010111) is notified.Furthermore, the communication apparatus 100 may not performnotification of a PMI list to be notified in addition to the bitsequence (010111). Here, it is assumed that as the number of PMIs to benotified to each PRB, a fixed value of 2 is used.

Therefore, in regard to the transmission system related to the firstembodiment, the communication apparatus 100 may further reduce theoverhead that is necessary for the notification while accommodating theUE, which is an object of the CoMP in which a proportion of a frequencyresource that is used in a cell is small, in a specific limited band.

Here, a CoMP UE is a UE that is an object of the CoMP. In addition,non-CoMP UE is a UE that is not an object of the CoMP.

In addition, in a system band shown in FIG. 13, description was madewith respect to an example in which the system band is equally dividedand a plurality of sub-bands having an equal bandwidth are defined, butit is not limited thereto. For example, the bandwidths to divide thesystem band may be different from each other. This case will bedescribed with reference FIG. 14. FIG. 14 shows a diagram illustratingan example (2) in which the sub-band number and whether or not PMInotification in the same sub-band is performed are notified with abitmap in the first embodiment.

For example, in a case where the UE that is an object of the CoMP andthe non-CoMP UE are effectively used with a frequency resource in asystem band, generally, the number of them is different in each case(the number of CoMP UEs <the number of non-CoMP UEs). Therefore, forexample, it is considered that the system band is divided in proportionto the number of CoMP UEs to generate the sub-band, and the frequencyresource is effectively used.

Here, as shown in FIG. 14, in regard to the transmission system relatedto the first embodiment, the system band is divided into two and two subsystem bands are defined. That is, a sub-band #0 is correlated with asub-band number (00). A sub-band #1 is correlated with a sub-band number(01). This system band and the system band shown in FIG. 13 aredifferent in that four equally spaced physical resource blocks PRB #0 toPRB #3 are included in the sub-band #0, but twelve equally spacedphysical resource blocks PRB #4 to PRB #15 are included in the sub-band#1 so as to unequally divide the system band.

In addition, in the system band shown in FIG. 14, only three physicalresource blocks PRB #1, PRB #2, and PRB #3, which are included in thesub-band #1 with which sub-band number (00) are correlated, are selectedas a PMI to be notified to other nodes.

That is, in the transmission system related to the first embodiment, thecommunication apparatus 100 selects the PMI to be notified to othernodes only in the sub-band #1 with which the sub-band number (00) iscorrelated. Furthermore, a bit sequence representing a frequencyresource position of the PMI to be notified to other nodes is made up of“sub-band number” and “whether or not the notification of the PMI in thesub-band is performed (bitmap)”. That is, as a bit sequence in which thesub-band number (00) corresponding to the sub-band #1 and the bitmap(0111) representing whether or not the notification of the PMI in thesub-band is performed are combined, (010111) is notified. Furthermore,the communication apparatus 100 may not perform notification of theselected PMI list in addition to this bit sequence (010111). Here, it isassumed that as the number of PMIs to be notified to each PRB, a fixedvalue of 2 is used.

Therefore, in regard to the transmission system related to the firstembodiment, the communication apparatus 100 may further effectivelyrealize the ICIC in the frequency domain and the spatial domain withsmall overhead.

In addition, in regard to a method of performing notification ofinformation of the sub-band number and the bitmap representing whetheror not the notification of the PMI in the sub-band is performed, the bitsequence representing the sub-band number may be notified with atransmission format which more hardly causes an error than the bitmapinformation representing whether or not the notification of the PMI inthe sub-band is performed. For example, a coding rate of errorcorrection code may be improved by treating the sub-band number as anMSB (Most Significant Bit). In addition, in regard to a high-levelmodulation (16QAM or the like), allocation may be made to a bit positionof constellation with high reliability. Therefore, the CoMP may bereliably operated among a plurality of nodes.

In addition, in regard to the notification of the information of thesub-band number and the bitmap representing whether or not thenotification of the PMI in the sub-band is performed, notification of aplurality of frequency resource numbers (for example, PRB numbers), atwhich the PMI in the sub-band is notified, may be performed.

For example, in regard to a case where the frequency resource is made upof 110 PRBs (a case where PRB numbers of 0 to 109 are expressed with 6bits), when the PRB numbers at which the PMI is notified are 5 and 20,“0000101 (=5)” and “00010100 (=20)” may be notified.

In addition, in regard to the notification of the information of thesub-band number and the bitmap representing whether or not thenotification of the PMI in the sub-band is performed, in a case wherethe frequency resources at which the PMI in the sub-band is notified arepresent in succession, an initiation number and a termination number ofthe frequency resources may be notified.

For example, in regard to a case where the frequency resources are madeup of 110 PRBs (a case where PRB numbers of 0 to 109 are expressed with7 bits), when the PRB numbers at which the PMI is notified are 5 to 15,“initiation number=0000101 (=5)” (“termination number=0001111 (=15)”)may be notified.

In addition, in regard to the notification of the information of thesub-band number and the bitmap representing whether or not thenotification of the PMI in the sub-band is performed, in a case wherethe frequency resources at which the PMI in the sub-band is notified arepresent in succession, an initiation (or termination) number of thefrequency resources, an absolute value of the length (bandwidth) of thesuccessive frequency resources may be notified.

For example, in regard to a case where the frequency resources are madeup of 110 PRBs (a case where PRB numbers of 0 to 109 are expressed with7 bits), when the PRB numbers at which the PMI is notified are 5 to 15,“initiation number=0000101 (=5)” (“termination number=0001111 (=15)”)and “length=0001010 (=10)” may be notified. In addition, in the case ofperforming notification of the frequency resource initiation number(termination number) and the length, the notified node may acquire thetermination number (initiation number) by adding the length to theinitiation number (by subtracting the length from the terminationnumber). In addition, an identifier (flag), which indicates thenotification of the initiation number or the termination number, may betransmitted in addition to the absolute value of the length (bandwidth)of the frequency resource.

In regard to the transmission system according to the first embodiment,the communication apparatus 100 may further reduce the overhead relatedto the position information of the frequency resource at which the PMIis notified while maintaining the ICI reduction effect due to theabove-described notification method of information of the sub-bandnumber and the bitmap representing whether or not PMI notification inthe sub-band is performed.

(Second Embodiment)

Next, a second embodiment will be described in detail with reference toFIG. 15. In regard to the transmission system according to thisembodiment, a communication apparatus according to the second embodimenthas at least the following characteristics (1) and (2).

(1) In response to the number of 1's (or 0's) of a binary indicator ofthe RNTP within a sub-band, which is made up of a plurality of resourceelements (REs), a plurality of sub-carriers, a plurality of PRBs, or thelike, an amount of precoding (beamforming) information (for example, thenumber of PMI lists) is controlled in band units.

(2) The larger the number of RNTP of 1's (0's) within the sub-band, thefurther the amount of the precoding (beamforming) information (forexample, the number of PMI lists) is increased (decreased).

Here, in regard to the transmission system according to the secondembodiment, an operation of the extended PMI list selecting unit 131 ofthe communication apparatus according to the second embodiment will bedescribed with reference to FIG. 15. In addition, other constituentelements are the same as those of the communication apparatus 100A inthe first modification example related to the first embodiment, andtherefore a description with respect to these will not be repeated.

FIG. 15 shows an example of an extended PMI list in the secondembodiment. FIG. 15 also shows a binary indicator of the RNTP for eachfrequency resource (for each of PRBs #0 to #8), which corresponds to theextended PMI list. In addition, FIG. 15 also shows a result of countingthe number of the binary indicators (0's or 1's) of the RNTP every threePRBs.

Furthermore, in an example of the extended PMI list shown in FIG. 15,for each band of 3 PRBs in which the number of binary indicators (0's or1's) of the RNTP is counted, (A) in a case where the number of PRBs inwhich the binary indicator of the RNTP is 1 (or 0) is 0 (or 3), thenumber of PMI lists to be notified is set to 0, (B) in a case where thenumber of PRBs in which the binary indicator of the RNTP is 1 (or 0) is1 (or 2), the number of PMI lists to be notified is set to 1, (C) in acase where the number of PRBs in which the binary indicator of the RNTPis 1 (or 0) is 2 (or 1), the number of PMI lists to be notified is setto 2, and (D) in a case where the number of PRBs in which the binaryindicator of the RNTP is 1 (or 0) is 3 (or 0), the number of PMI liststo be notified is set to 3.

For example, as shown in FIG. 15, in a band made up of three PRBs #0 to#2, since the number of PRBs in which the binary indicator of the RNTPis 1 (or 0) is 2 (or 1), the communication apparatus allows the extendedPMI list selecting unit 131 to select two PMI lists (PMI #0 and PMI #1)to be notified.

That is, in regard to the transmission system according to thisembodiment, the larger (smaller) the number of the frequency resources(PRBs in FIG. 15) in which the binary indicator of the RNTP is 1 (or 0)in the band of the sub-band, the further the communication apparatusaccording to the second embodiment increases (decreases) the amount ofthe precoding (beamforming) information (for example, the number of PMIlists).

As described with reference to FIG. 15, the communication apparatusaccording to the second embodiment variably controls an amount of theprecoding (beamforming) information (for example, the number of PMIlists) in response to the number of 1's (or 0's) of the binary indicatorof the RNTP within the sub-band, which is made up of the plurality ofresource elements (REs), the plurality of sub-carriers, the plurality ofPRBs, or the like, and notifies other nodes of the amount ofinformation, and thereby realizes the ICIC of the frequency domain andthe spatial domain.

Therefore, the communication apparatus according to the secondembodiment may further reduce the overhead related to the precoding(beamforming weight (for example, the number of PMI lists)) informationthat is notified over the backhaul while maintaining the ICI reductioneffect due to the coordinated CB between nodes.

(Third Embodiment)

Next, a third embodiment will be described in detail.

In regard to a transmission system according to the third embodiment, anoperation of an extended PMI list selecting unit 131 of a communicationapparatus 600 will be described with reference to FIGS. 16A and 16B. Inaddition, other constituent elements are the same as those of thecommunication apparatus 100A according to the first modification exampleof the first embodiment, and therefore a description thereof will not berepeated. FIGS. 16A and 16B show an example of an extended PMI list inthe third embodiment.

In regard to the transmission system according to this embodiment, thecommunication apparatus 600 has at least the following characteristics(1) and (2).

(1) A plurality of threshold values for each cell (component carrier orthe like) that is used at the time of determining a binary indicator ofRNTP are correlated with an amount of precoding (beamforming)information (for example, the number of PMI lists).

(2) The larger (smaller) the threshold value of the RNTP, the furtherthe amount of the precoding (beamforming) information (for example, thenumber of PMI lists) is increased (decreased).

Here, since the threshold value of the RNTP is set to a plurality ofvalues for each node, implication of the RNTP (0 or 1) is differentdepending on the value of the threshold value. A case in which thethreshold value of the RNTP is large and the binary indicator of theRNTP is 1, means that transmission signal power is significantly large.In addition, a case in which the threshold value of the RNTP is middleand the binary indicator of the RNTP is 1 means the transmission signalpower is large.

Therefore, in this embodiment, as described below, the plurality ofthreshold values for each cell (component carrier or the like), whichare used at the time of determining the binary indicator of the RNTP,are correlated with the amount of the precoding (beamforming)information (for example, the number of the PMI lists). That is, (A) ina case where the threshold value of the RNTP is large and the binaryindicator of the RNTP is 1, the number of PMI lists that is notified isset to be large. (B) In a case where the threshold value of the RNTP issmall and the binary indicator of the RNTP is 1, the number of PMI liststhat is notified is set to be small.

Therefore, the fact that the implication of the binary indicator of theRNTP is different depending on the magnitude of the threshold value ofthe RNTP may be reflected on the amount of information. Therefore, inregard to the transmission system according to this embodiment, thecommunication apparatus 600 may notify other nodes of a relativelyaccurate amount of the precoding (beamforming) information (for example,the number of PMI lists). In addition, in regard to the transmissionsystem according to this embodiment, since the communication apparatus600 may set the number of PMIs, which is necessary to a minimum, inresponse to a magnitude of an amount of interference applied to othercells for each cell (component carrier or the like), the communicationapparatus 600 may further reduce the overhead related to the PMIinformation while reducing the ICI.

Here, as described above, one component carrier represents any largefrequency band such as 20 MHz.

(Fourth Embodiment)

In the above-described embodiment, description was made with respect toa method in which in response to the indicator of 1 (0) of the RNTP foreach frequency resource, an amount of the precoding (beamforming)information (for example, the number of PMI lists) in a correspondingband is made to increase (decrease) and then this information isnotified to other nodes. Therefore, in regard to a transmission systemaccording to the fourth embodiment, a method of combining the indicatorof the RNTP of LTE Rel. 8 to this embodiment will be described withreference to FIG. 17. FIG. 17 shows a diagram illustrating a method ofnotifying other nodes of the indicator of the RNTP and the PMI list atthe same time.

In FIG. 17, the indicator of the RNTP, and the selected PMI list that isselected by the extended PMI list selecting unit 131 in theabove-described embodiment are notified from the communication apparatus600 to other nodes at the same time. For explanation, in FIG. 17, thecommunication apparatus 600 is expressed as NodeB_1 and another node isexpressed as NodeB_2.

In addition, in FIG. 17, two pieces of information (the indicator of theRNTP and the PMI list) are notified at the same time at timings of timesT1, T3, and T5. Therefore, since the NodeB_2 may acquire other-cellinterference information in a frequency domain and a spatial domain fromthe NodeB_1, the NodeB_2 may perform the ICIC control of the frequencydomain, or the frequency domain and spatial domain in a flexible manner.

However, since the NodeB_1 notifies the NodeB_2 of information of themagnitude of the transmission signal power for each frequency resourcein surplus at times T1, T3, and T5 at which the two pieces ofinformation (the indicator of the RNTP and the PMI list) are notified,the above-described method has another problem in that traffic on thebackhaul is made to be heavy.

This is because the amount of information of the PMI list for eachfrequency resource is determined on the basis of the magnitude of thetransmission signal power of the frequency resource in a correspondingband and therefore the abundance in the amount of information of the PMIlist implicitly represents the magnitude of the transmission signalpower of the frequency resource in a corresponding band. Therefore, attimes T1, T3, and T5, the NodeB_2 acquires the information of themagnitude of the transmission signal power of the frequency resource ofthe NodeB_1 from two pieces of information of the indicator of the RNTPand the PMI list in a duplicating manner.

Therefore, in a modification example of this embodiment, thecommunication apparatus 600 make a notification cycle different in amethod of notifying other nodes of information of transmission power(density), (normalized) transmission signal energy (density), or amagnitude (good or bad) of a communication quality for each frequencyresource, and information of precoding (beamforming) (for example, thenumber of PMI lists) at a corresponding frequency resource position.

FIG. 18 shows a block diagram of the communication apparatus 600. Thecommunication apparatus 600 shown in FIG. 18 includes a receptionprocessing unit 101, a control information extracting unit 103, anextended PMI list storing unit (for a serving node) 105, a precodingweight determining unit 107, a data information transmission processingunit 109, a control information transmission processing unit 111, areference signal transmission processing unit 113, a scheduler unit 115,a transmission signal power control unit 117, a radio transmissionprocessing unit 119, an RNTP indicator generating unit 121, a controlunit 123, a radio reception processing unit 125, a control informationextracting unit 127, an extended PMI list storing unit (for other nodes)129, an extended PMI list selecting unit 131, a control informationgenerating unit 133, a transmission processing unit 135, and atransmission and reception antenna 137.

Here, an operation of the communication apparatus 600 shown in FIG. 18is different from the operation of the communication apparatus 100Ashown in FIG. 6 is in an operation of the control unit 123 and anoperation of the extended PMI list selecting unit 131. Hereinafter, inthis embodiment, the operation of the control unit 123 and the operationof the extended PMI list selecting unit 131 will be mainly described.

In regard to a transmission system according to the fourth embodiment, atiming at which the indicator of the RNTP and the PMI list are notifiedwill be described with reference to FIG. 19. FIG. 19 shows a diagramillustrating a method (1) of notifying other nodes of the RNTP and thePMI list in such a manner that a notification timing of the RNTP and anotification timing of the PMI are made different from each other.

In addition, for explanation, in FIG. 19, the communication apparatus600 is expressed as NodeB_#1 (serving cell) and another node that is anotification destination of the indicator of the RNTP and the PMI listis expressed as NodeB_#2 (non-serving cell).

As shown in FIG. 19, as a notification timing that is set by the controlunit 123, (1) a notification timing of the RNTP from the NodeB_#1 to theNodeB_#2 includes T1, T3, and T5, and (2) a notification timing of thePMI list from the NodeB_#1 (serving cell) to the NodeB_#2 (non-servingcell) includes T2 and T4. In addition, PMI information of the PMI listat T2 and T4 is PMI information that is selected from futuretransmission signal power information (indicator of RNTP) at points oftime T2 and T4 on the basis of any method of the above-describedembodiments and modification example.

That is, in the transmission system according to the fourth embodiment,the communication apparatus 600 allows the control unit 123 to set bothof the notification timing of the RNTP from the NodeB_#1 (serving cell)to the NodeB_#2 (non-serving cell) and the notification timing of thePMI list from the NodeB_#1 (serving cell) to the NodeB_#2 (non-servingcell) in such a manner that these notification timings are differentfrom each other.

In addition, since the extended PMI list selecting unit 131 determinesthe information of the number of PMI lists on the basis of the magnitude(the indicator of the RNTP (0 or 1)) of future transmission signal powerat each point of time, the NodeB, which receives both of theinformation, may implicitly learn, from an amount of the precoding(beamforming) information (for example, the number of PMI lists) at afrequency resource position, “information of transmission power(density) of a corresponding cell at the corresponding frequencyresource, (normalized) transmission signal energy (density), or amagnitude (good or bad) of a communication quality” that is informationof a magnitude of other-cell interference power.

As shown in FIG. 19, for example, the NodeB_#2 is not notified of theRNTP information at time T2 from the NodeB_#1, but the NodeB_#2 mayimplicitly learn, from the PMI information notified from the NodeB_#1 attime T2, “information of transmission power (density) of a correspondingcell at the corresponding frequency resource, (normalized) transmissionsignal energy (density), or a magnitude (good or bad) of a communicationquality” that is information of a magnitude of other-cell interferencepower.

Therefore, at all of the timings at which the information of the RNTP orthe PMI list is received, the NodeB_#2 may acquire the information ofthe magnitude of the interference power from other cells (node_#1).Therefore, this information may be used for CS.

In addition, in this embodiment, the communication apparatus 600 mayallow the control unit 123 to set the notification cycle of theinformation of precoding (beamforming) (for example, the number of PMIlists) to be longer than the notification cycle of the information oftransmission power (density), (normalized) transmission signal energy(density), or the magnitude (good or bad) of a communication quality foreach frequency resource. A description will be made with respect to thiscase with reference to FIG. 20. FIG. 20 shows a diagram illustrating amethod (2) of notifying other nodes of the RNTP and the PMI list in sucha manner that the notification cycle of RNTP and the notification cycleof a PMI list are made to be different from each other.

As shown in FIG. 20, the control unit 123 sets the notification cycle ofthe transmission power from the NodeB_#1 (serving cell) to the NodeB_#2(non-serving cell) every T-rntp, and sets the notification cycle of anextended PMI from the NodeB_#1 to the NodeB_#2 to T_pmi (T_rntp≦T_pmi).In addition, PMI information of the PMI list at T2 and T6 is PMIinformation that is selected from future transmission signal powerinformation (indicator of RNTP) at points of time T2 and T6 on the basisof any method of the above-described embodiments and modificationexample.

Therefore, in this embodiment, the communication apparatus 600preferentially performs notification of the “information of transmissionpower (density) of a corresponding cell at the corresponding frequencyresource, (normalized) transmission signal energy (density), or amagnitude (good or bad) of a communication quality” that is informationof a magnitude of other-cell interference power with high frequencycompared to the information of the RNTP or the PMI list, such that thenotification of the information of a case in which the other-cellinterference power is small (useless precoding (beamforming) in afrequency resource that is not necessary for the coordinated ICIC) (forexample, the number of PMI lists) may be avoided. That is, the overheadmay be reduced.

In addition, the NodeB_#2 that is a reception node may receive the“information of transmission power (density) of a corresponding cell atthe corresponding frequency resource, (normalized) transmission signalenergy (density), or a magnitude (good or bad) of a communicationquality” that is information of a magnitude of other-cell interferencepower with high frequency. Therefore, since only a UE of a serving cellmay be considered at a frequency resource in which the other-cellinterference power is small, precoding (beamforming) may be performed ina flexible manner without performing a useless calculation related toother-cell interference.

In addition, in the above-described embodiment, description was madewith respect to a case in which the communication apparatus 600 allowsthe control unit 123 to set the notification cycle of the information ofprecoding (beamforming) (for example, the number of PMI lists) to belonger than the notification cycle of the information of transmissionpower (density), (normalized) transmission signal energy (density), orthe magnitude (good or bad) of a communication quality for eachfrequency resource. Conversely, the notification cycle of theinformation of precoding (beamforming) (for example, the number of PMIlists) may be set to be shorter than the notification cycle of theinformation of transmission power (density), (normalized) transmissionsignal energy (density), or the magnitude (good or bad) of acommunication quality for each frequency resource.

For example, to avoid a dynamic variation in the other-cellinterference, a node may use a transmission power control method inwhich transmission is performed with constant power for a given timeperiod, and in this case, the degree of importance of the information offuture transmission signal power (indicator of the RNTP) becomes lowerthan the degree of importance of the precoding (beamforming) (forexample, the number of PMI lists) information. Therefore, the precoding(beamforming) may be operated among a plurality of cells in an effectivemanner under a circumstance in which the dynamic variation intransmission signal power (other-cell interference when seen from othercells) is small by using the above-described method.

In addition, in this embodiment, the communication apparatus 600 mayonly transmit the PMI list to the NodeB_#2 without transmitting theindicator of the RNTP to the NodeB_#2. Therefore, as described above, inthe transmission system according to this embodiment, since thecommunication apparatus 600 may implicitly learn information oftransmission signal power (magnitude) of other cells from the amount ofinformation (for example, the number of PMI lists) of the extended PMIlist, the overhead related to the amount of control information of theRNTP may be eliminated.

In addition, in each of the above-described embodiments, thecommunication apparatuses (base stations (NodeBs)) are adopted as nodesthat coordinate the precoding (beamforming) information with each other,but it is not limited thereto. For example, a macro station (NodeB), amicro station (NodeB), a Pico station (NodeB), a Home station (NodeB),an overhang antenna (RRE: Remote Radio Head, RRE=Remote RadioEquipment), and the like may be exemplified, and the communicationapparatuses may be adopted to these. In addition, items of userequipment may be set as nodes, and a backhaul between the items of userequipment may be connected in a radio manner and may be applied tocoordination between the items of user equipment. In this manner, thesame effect as the above-described embodiments may be obtained.

In addition, in each of the above-described embodiments, description wasmade with respect to a case in which the backhaul between nodes isconnected with a wire network such as X2, but the backhaul may beapplied to a configuration in which the coordinated nodes are connectedwith a radio network. For example, the backhaul may be applied tobetween a relay node and the macro NodeB, between relays, or the like,in which the backhaul is configured with a radio manner. In this manner,the same effect as the above-described embodiments may be obtained.

In addition, in each of the above-described embodiments, description wasmade with respect to a case in which other nodes are notified of theprecoding (beamforming) information in a physical resource (asub-carrier, a resource element, a resource block, or the like) in thefrequency domain, but it is not limited thereto. It may be applied toother physical resources such as time, code, . . . , domain, or thelike, instead of the frequency. In this manner, the same effect as eachof the above-described embodiments may be obtained.

In addition, in each of the above-described embodiments, description wasmade with respect to an example in which other nodes are notified of theprecoding (beamforming weight) information in a physical resource (asub-carrier, a resource element, a resource block, or the like) of thefrequency domain, but it is not limited thereto. For example, it may beapplied with respect to a logical resource (for example, a virtualsub-carrier, a virtual resource element, a virtual resource block, orthe like). In this manner, the same effect as each of theabove-described embodiments may be obtained while restrictions of aphysical resource that transmits a transmission signal are not imposed.

In addition, in each of the above-described embodiments, the informationof the transmission signal power (for example, RNTP) may be notifiedsimultaneously together with the information of the extended PML In thismanner, an appropriate precoding weight may be selected from thenotified extended PMI information by considering the information of thetransmission signal power in other nodes. That is, since the informationof the other-cell interference power in the frequency domain, and theprecoding (beamforming) information of the other-cell interference inthe spatial domain may be acquired at the same time, the ICIC control ofthe frequency domain and the spatial domain may be performed in aflexible manner.

In addition, in each of the above-described embodiments, description wasmade with respect to a case in which successive frequency resources areset as a group and the extended PMI with respect to this group isnotified, but not-successive frequency resources may be set as a groupand the extended PMI may be notified.

In addition, in each of the above-described embodiments, a PMI otherthan a worst (best) PMI may be notified without notifying the worst(best) PMI as the extended PMI information such as best (worst) PMI. Forexample, a second worst (best) PMI is notified. In this manner, inregard to the entirety of a plurality of cells, when performingnotification of the second worst (best) PMI instead of the worst (best)PMI, this may maximize throughput in the entirety of the plurality ofcells from a viewpoint of total optimization, and the operation may beperformed at this case in an effective manner.

In addition, in each of the above-described embodiments, description wasmade with respect to a case in which the PMI is notified as beamforming(precoding) information, but it is not limited thereto. In the case ofperforming notification of explicit channel information such as acovariance matrix of a propagation channel (or a transmission signal ora reception signal) and a channel matrix, the number of quantizationbits of the information may be correlated with information or the like(for example, an RNTP value) about the magnitude of the transmissionsignal power or the like. In this manner, the same effect as thatdescribed above may be obtained.

In addition, in each of the above-described embodiments, the number ofthe extended PMIs that is notified (or granularity) may be changed incorrelation with the number of antenna ports (codebook size) for eachnode. For example, in a case where the number of the transmissionantenna ports (codebook size) of the node (cell) is large, accompanyingthis, the amount of the beamforming (precoding) information and thenumber of PMIs that is notified may be increased. In this manner, in thecase of other configurations such as the number of antenna ports isdifferent in each node, the optimization may be made in the entirety ofsystem.

In addition, in each of the above-described embodiments, description wasmade with respect to a configuration in which any one of information ofthe best PMI (PMI whose use by other cells is limited (prohibited) andnot encouraged) or information of worst PMI (PMI whose use by othercells is encouraged) is notified for each frequency resource, but it isnot limited thereto. The two pieces of information may be transmitted atthe same time with any specific same frequency resource that isselected. FIGS. 21A and 21B show an example thereof. FIGS. 21A and 21Bare diagrams illustrating a method of transmitting two pieces ofinformation at the same time with the specific same frequency resource.

FIG. 21A shows a case of performing notification of best and worst PMIlists of PRB numbers of #0 and #3 and position information ofcorresponding frequency resources. In addition, FIG. 21B shows a case ofperforming notification of the number of the best and worst PMI lists,which is correlated with the information of the transmission signalpower, and the position information of the corresponding frequencyresources, and this case corresponds to a case of performingnotification of the best and worst PMI lists of PRB numbers of #0 and #3in which the transmission signal power is large and the positioninformation of corresponding frequency resources.

In this manner, even in a case where a transmission mode of the CoMP isdifferent in each frequency resource for each cell, for example, even ina case where a CB mode is adopted in a cell 1 within an adjacent node,and JP is adopted in a cell 2 within the adjacent node as the CoMP, itis possible to cope with this case at the same time.

In addition, in each of the above-described embodiments, description wasmade with respect to a case in which a serving cell transmits anextended PMI (beamforming/precoding) request signal toward a UE that isconnected to a serving cell, and the UE received the signal selects, forexample, a PMI list (PMI list whose use by other cells is restricted(prohibited) and is recommended not to be encouraged), which generateslarge other-cell interference with respect to the serving UE, and feedsback this information to the serving cell.

However, the UE that is connected to the serving cell may followexamples described below while not transmitting the extended PMI(beamforming/precoding) request signal. For example, as is the case withLTE Rel. 8, the serving cell transmits the PMI feedback request signalwith respect to a UE in a serving cell (transmits a PMI (for example, abest PMI) request signal that is recommended to be used with respect tothe serving UE), and the UE feeds back this information to the servingcell. The serving cell generates a list of the best PMIs that is fedback for each frequency band. In addition, in lists made up of aplurality of best PMIs, only a PMI, which corresponds to the CoMP mode,is selected as a PMI list to be notified to other nodes for eachfrequency band (in other words, a PMI of a non-CoMP mode is not selectedas a PMI to be notified to other nodes). In addition, only the PMI thatis selected for each frequency band is notified to other nodes. Withthis configuration, the same effect as that described above may beobtained while maintaining a feedback mechanism of LTE Rel. 8, that is,backward compatibility.

In addition, in each of the above-described embodiments, other nodes mayalso be notified of a threshold value of the RNTP that is used for eachcell (component carrier) of each node. In this manner, the node, whichreceives information of precoding (beamforming) and the information ofthe PMI list, may independently determine the magnitude of an amount ofinterference from other cells from a fact in which implication of theindicator (0 or 1) of the RNTP is different depending on the magnitudeof the threshold value (for example, since the maximum power that ispermitted is different in NodeB, Relay, and Home NodeB, the receptionnode may independently determine the magnitude of the ICI from thepermitted maximum power and the threshold value of the RNTP in anaccurate manner). Therefore, since this may be used in determiningwhether to take the information of precoding (beamforming) and theinformation of the PMI list to what extent or not to take thisinformation, the flexibility in the selection of the PMI list may befurther increased.

In addition, in each of the above-described embodiments, in a case wherethe amount of the beamforming/precoding information (the number of theextended PMIs that is notified) and the information of the magnitude ofthe transmission signal power are correlated with each other, and theRNTP and the beamforming/precoding (extended resource) information foreach frequency resource is notified, since the information of thetransmission power to other cells may be implicitly learned from theamount of the beamforming/precoding information (the number of extendedPMIs that is notified), the information of frequency resource positionto which the information of beamforming/precoding (extended PMI)corresponds may not be transmitted. Therefore, the overhead may befurther reduced.

In addition, in each of the above-described embodiments, description wasmade with respect to a method of performing notification of theprecoding (for example, PMI) information or beamforming weightinformation between nodes with the CoMP of the DL made as an object, butin regard to the CoMP of UL (uplink), this description may be alsosimilarly applied to a method of performing notification the precoding(for example, PMI) information or the beamforming weight informationover a backhaul in coordinated beamforming between UEs that areconnected to a plurality of cells. Therefore, the same effect as each ofthe above-described embodiment may be obtained.

In addition, in the above-described embodiments, description was madewith respect to an antenna, but this description may be also similarlyapplied to an antenna port. The antenna port represents a logicalantenna that is made up of one or a plurality of physical antennas. Thatis, the antenna port does not necessarily represent only one physicalantenna, and the antenna port may represent an array antenna that ismade up of a plurality of antennas.

For example, in LTE, the number of physical antennas making up theantenna port is not defined, and the antenna port is defined with aminimum unit in which a base station may transmit a different referencesignal. In addition, the antenna port may be defined with a minimum unitthat multiplies weighting of a precoding vector.

In addition, each functional block that is used in each of theabove-described embodiments is typically realized by an LSI that is anintegrated circuit. The functional blocks may be individually composedof a single chip, and the functional blocks may be composed of a singlechip so as to include parts or the entirety of the functional blocks.Here, the LSI is exemplified, but this may be called an IC, a systemLSI, a super LIS, or an ultra LSI depending on the degree ofintegration.

In addition, a type of an integrated circuit is not limited to the LSI,and the integrated circuit may be realized by a dedicated circuit or ageneral-purpose processor. An FPGA (Field Programmable Gate Array),which may be programmed after manufacturing the LSI, or a reconfigurableprocessor in which connection or setting of circuit cells inside the LSIis may be reconfigured may be used.

In addition, when a technology of integrated circuits that substitutesthe LSI appears according to development of a semiconductor technologyor a separate technology derived therefrom, the integration of thefunctional block may be naturally performed by using this technology.Application to biotechnology or the like may be possible.

The invention was described in detail with reference to specificembodiments, but it should be understood by those skilled in the artthat various changes and modifications may be made without departingfrom the sprit and scope of the invention.

The present application is based upon Japanese Patent Application No.2010-003332 filed on Jan. 8, 2010, the contents of which areincorporated herein by reference.

INDUSTRIAL APPLICABILITY

The communication apparatus and communication method according to theinvention have an effect of reducing overhead related to information,which are notified over a backhaul, while maintaining an ICI reductioneffect by DL coordinated CoMP (CB, JP, or the like) among a plurality ofnodes, and therefore they are effective as a radio communicationapparatus or the like.

REFERENCE SIGNS LIST

100, 100A, 600: Communication apparatus

101: Reception processing unit

103: Control information extracting unit

105: Extended PMI list storing unit (for a serving node)

107: Precoding weight determining unit

109: Data information transmission processing unit

111: Control information transmission processing unit

113: Reference signal transmission processing unit

115: Scheduler unit

117: Transmission signal power control unit

119: Radio transmission processing unit

121: Indicator generating unit

123: Control unit

125: Radio reception processing unit

127: Control information extracting unit

129: Extended PMI list storing unit (for other nodes)

131: Extended PMI list selecting unit

133: Control information generating unit

135: Transmission processing unit

137: Transmission and reception antenna

What is claimed is:
 1. A communication node comprising: a receiver thatreceives communication quality information from user equipments in anown cell; a selector that selects a particular frequency resourceposition corresponding to first information regarding a usage of acoordinated multi-point (CoMP) mode, the particular frequency resourceposition being a frequency resource position for transmitting the firstinformation to another communication node; a generator that generatesfrequency resource position information which represents the particularfrequency resource position and another frequency resource position bydifferent values on a frequency resource basis; and a transmitter thattransmits the first information, the frequency resource positioninformation, the communication quality information, and a cell ID towhich the frequency resource position corresponds, to anothercommunication node in another cell.
 2. The communication node accordingto claim 1, wherein the transmitter transmits the first information, thefrequency resource position information and the cell ID in a group foreach of a plurality of transmit-destination cells.
 3. The communicationnode according to claim 1, wherein the frequency resource positioninformation includes at least one of the following: a bit map in a unitof PRB; an initiation PRB and a termination PRB; and the initiation PRBor the termination PRB, and a bandwidth of a frequency resource.
 4. Thecommunication node according to claim 1, wherein the transmittertransmits the first information, the frequency resource positioninformation and the cell ID via a backhaul, wherein the backhaul is anX2 interface.
 5. The communication node according to claim 1, whereinthe transmitter transmits the first information and the frequencyresource position information to said other communication nodeperiodically.
 6. The communication node according to claim 1, whereinthe particular frequency resource position is determined based on one ofa transmission mode for each frequency resource, position information ofthe user equipments and transmission power information for eachfrequency resource, with regard of the first information.
 7. Thecommunication node according to claim 1, wherein the first informationis information regarding prohibition, restriction, encouragement, ornon-encouragement of use of the CoMP mode in another cell or adjacentcommunication nodes.
 8. The communication node according to claim 1,wherein the frequency resource position information includes whether ornot the first information is present for each frequency resource.
 9. Acommunication method performed in a communication node, the methodcomprising: receiving communication quality information from userequipments in an own cell; selecting a particular frequency resourceposition corresponding to first information regarding a usage of acoordinated multi-point (CoMP) mode, the particular frequency resourceposition being a frequency resource position for transmitting the firstinformation to another communication node; generating frequency resourceposition information which represents the particular frequency resourceposition and another frequency resource position by different values ona frequency resource basis; and transmitting the first information, thefrequency resource position information, the communication qualityinformation, and a cell ID to which the frequency resource positioncorresponds, to another communication node in another cell.
 10. Thecommunication method according to claim 9, wherein the firstinformation, the frequency resource position information and the cell IDare transmitted in a group for each of a plurality oftransmit-destination cells.
 11. The communication method according toclaim 9, wherein the frequency resource position information includes atleast one of the following: a bit map in a unit of PRB; an initiationPRB and a termination PRB; and the initiation PRB or the terminationPRB, and a bandwidth of a frequency resource.
 12. The communicationmethod according to claim 9, wherein the first information, thefrequency resource position information and the cell ID are transmittedvia a backhaul, wherein the backhaul is an X2 interface.
 13. Thecommunication method according to claim 9, wherein the first informationand the frequency resource position information are transmitted to saidother communication node periodically.
 14. The communication methodaccording to claim 9, wherein the particular frequency resource positionis determined based on one of a transmission mode for each frequencyresource, position information of the user equipments and transmissionpower information for each frequency resource, with regard of the firstinformation.
 15. The communication method according to claim 9, whereinthe first information is information regarding prohibition, restriction,encouragement, or non-encouragement of use of the CoMP mode in anothercell or adjacent communication nodes.
 16. The communication methodaccording to claim 9, wherein the frequency resource positioninformation includes whether or not the first information is present foreach frequency resource.